'Hump' was the US nickname rather than formal codename for the air route created to take off from India and overfly the eastern end of the Himalayan mountains for the supply of the US forces in China as well as the Chinese nationalist armed forces of Generalissimo Chiang Kai-shek (April 1942/November 1945).

Creating an airlift operation of this size and difficulty, given the terrain its aircraft would have to cross and weather conditions with which it would have to cope, was a formidable challenger fore the US Army Air Forces in 1942: the service had no units trained or equipped for the movement of cargo, and there were no airfields in the China-Burma-India Theater to accommodate the large number of transport aircraft which would be required. Flying over the Himalayan mountains was extremely dangerous, especially as their were no reliable charts, no radio navigation aids, and little information about the weather.

The task was initially allocated to Major General Lewis H. Brereton’s US 10^th Army Air Force, and then to Brigadier General (eventually Lieutenant General Harold L. George’s Air Transport Command. As the USAAF lacked all but a rudimentary airlift experience as a basis for planning in 1942, it assigned commanders who had been key figures in the establishment of the ATC in 1941/42 to build and direct the operation, these men including former civilians with extensive experience in civil air transport. The organisations responsible for implementing what was at first known as the India-China Ferry were the Assam-Burma-China Command (April/July 1942) and the India-China Ferry Command (July/December 1942) of the 10^th AAF, and the ATC’s India-China Wing (December 1942/June 1944) and India-China Division (July 1944/November 1945).

The airlift began in April 1942, after the Japanese had blocked the Burma Road, and continued daily to August 1945, when the effort was steadily reduced. The airlift drew most of its officers, men and equipment from the USAAF, but these were augmented by men of the British-led forces in India, Burmese labour detachments, and an air transport section of the Chinese National Aviation Corporation. The airlift ended in November 1945 after the operation had completed the return of US personnel from China.

The 'Hump' airlift delivered about 650,000 tons of matériel to China at a major cost in men and aircraft during its 42-month history.

The need for the Burma Road and, once this had been closed, the 'Hump' airlift resulted from the 2^nd Sino-Japanese War (1937/45) and Japanese operations in French Indo-China (1940), which closed all the sea and rail access routes available to the Western world for the supply of matériel to China. The exceptions were that through Turkestan in the USSR, and that access was ended by the signature of the Soviet/Japanese Neutrality Pact in April 1941, and the Burma Road. The rapid success of Japanese military operations in South-East Asia early in 1942 threatened this lifeline and thus China’s continued participation in the war. Its commitment in China required Japan to commit more than one million troops, who might otherwise have been available to oppose future Allied operations in the Pacific and South-East Asia, and it was this fact which prompted discussion, as early as January 1942, of an air cargo service from north-eastern India. The Chinese nationalist foreign minister, T. V. Soong, estimated that 12,000 tons of matériel could be delivered each month by air from India if 100 aircraft of the Douglas C-47 Skytrain type were committed to an airlift.

On 25 February 1942 President Franklin D. Roosevelt wrote to General George C. Marshall, the US Army chief-of-staff, that 'it is of the utmost urgency that the pathway to China be kept open', and committed 10 Douglas C-53 Skytrooper transport aircraft for Lend-Lease delivery to CNAC, so increasing its transport aircraft strength to 25. When the 10^th AAF opened its headquarters in New Delhi in March 1942, it was assigned the responsibility of developing an India-China Ferry using both US and Chinese aircraft. Although never given command authority over aircraft or personnel, the officer responsible for the India-China Ferry was the 10^th AAF’s chief-of-staff Brigadier General Earl L. Naiden, who held that responsibility until the middle of August.

From the start, the air route was predicated on the establishment of two branches, unofficially deemed 'commands': a Trans-India Command from India’s western ports to Calcutta, where cargo would be trans-shipped by rail to Assam, and an Assam-Burma-China Command operating from bases in Assam to southern China. The scheme was initially predicated on the Allies holding northern Burma so that Myitkyina could be used as an offloading terminal from which supplies could be despatched by barge down the Irrawaddy river to Bhamo and transfer to the Burma Road. On 8 May 1942 the Japanese seized Myitkyina, however, and coupled with the loss of Rangoon this effectively cut Allied access to the Burma Road. In order to maintain the uninterrupted supply to China, Allied leaders agreed to organise a continual aerial resupply effort directly between Assam and Kunming in the south-western Chinese province of Yunnan.

The 10^th AAF’s efforts were hampered by the constant diversion of men and aircraft to Egypt, where there was a threat that the Italians and Germans might be able to seize the Suez Canal. The 10^th AAF’s Air Service Command personnel were still en route by ship from the USA, forcing it to obtain aircraft and personnel for the India-China Ferry from any available source. Pan American World Airways provided 10 Douglas DC-3 transports from its trans-Africa subsidiary and flight crews to outfit the new operation, but another 25 DC-3 transports were requisitioned from airlines in the USA could not be moved to India for lack of crews and were later integrated into the complement of the first transport group committed to the airlift.

The command structure of the India-China Ferry was divided after senior officers in both India and Burma made claims for jurisdiction: part of the authority was allocated to Lieutenant General Joseph W. Stilwell in his capacity as CBI theatre commander, and part remained with the 10^th AAF, which had also been ordered by Marshall to co-operate whenever requested by the British for the defence of India. The movement by ground transport of supplies arriving from the USA at the western port of Karachi to the airfields, as well as the construction of the infrastructure required to support the operation, was the responsibility of the US Army’s Services of Supply, commanded in the CBI theatre by Major General Raymond A. Wheeler. The airlift was the final leg of a journey of 12,000 miles (19300 km) from Los Angeles, California, to China and often took four months.

On 23 April 1942, Colonel Caleb V. Haynes, a prospective bombardment group commander, was assigned to command the Assam-Kunming branch of the India-China Ferry, dubbed the Assam-Burma-China Ferry Command. Colonel Robert L. Scott, a fighter pilot awaiting posting to China, was assigned as his operations officer and one month later became his executive officer. Haynes was a fortuitous choice to be the airlift’s first commander as he had been a key subordinate of Brigadier General Robert Olds. Olds had established the Air Corps Ferrying Command in June 1941 and pioneered overseas military air transport, including use of the South Atlantic air route by which aircraft, personnel, and cargo reached India from the USA. At the time the India-China Ferry was conceived, however, the Air Corps Ferrying Command was not prepared to plan, control or execute such an operation: its formal organisation was minimal, it had no units of its own, and its few aircraft were committed to establishing air transport routes. By June, though, the expansion and reorganisation of the Air Corps Ferrying Command had begun as part of the effort leading to the command’s re-establishment on 1 July as the Air Transport Command.

The first mission 'over the Hump' was flown on 8 April 1942 when, flying from the British airfield at Dinjan in Assam, Lieutenant Colonel William D. Old led a pair of the borrowed DC-3 aircraft to ferry 8,000 US gal (30,285 litres) of aviation fuel for the planned refuelling of the North American B-26 Mitchell medium bombers used in 'Conceal', the carrier-launched attack on Japan led by Lieutenant Colonel James H. Doolittle in April 1942. The collapse of Allied resistance in northern Burma in May 1942 meant further diversion of the already minuscule air effort. The ABC Ferry Command resupplied Stilwell’s retreating Chinese forces and evacuated its wounded, while establishing a regular air service to China using 10 borrowed DC-3, three USAAF C-47 and 13 CNAC C-53 and Douglas C-39 aircraft. Only two-thirds of the aircraft were serviceable at any time. Dinjan was within range of Japanese day fighters now based at Myitkyina, forcing all maintenance to be undertaken at night and the take-off of the unarmed transport aircraft before dawn. The threat of interception also forced the ABC Ferry Command to fly a difficult 500-mile (800-km) route to China over the eastern Himalayan mountains, which came to be known as the 'high hump' or just 'the Hump'.

The official history of the AAF states that 'The Brahmaputra valley floor lies 90 feet (27 m) above sea level at Chabua. From this level the mountain wall surrounding the valley rises quickly to 10,000 feet (3,000 m) and higher. Flying eastward out of the valley, the pilot first topped the Patkai Range, then passed over the upper Chindwin River valley, bounded on the east by a 14,000-foot (4,300 m) ridge, the Kumon Mountains. He then crossed a series of 14,000-16,000-foot (4,300-4,900m) ridges separated by the valleys of the West Irrawaddy, East Irrawaddy, Salween, and Mekong Rivers. The main ''Hump'', which gave its name to the whole awesome mountainous mass and to the air route which crossed it, was the Santsung Range, often 15,000 feet (4,600 m) high, between the Salween and Mekong Rivers. East of the Mekong the terrain became decidedly less rugged, and the elevations more moderate as one approached the Kunming airfield, itself 6,200 feet (1,900 m) above sea level.'

The spate of problems suffered with the Indian railway system meant that aircraft assigned to the airlift often carried their cargo all the way from Karachi to China, while much cargo took as long to reach Assam from Karachi as the two-month journey by ship from the USA. India’s road and river systems were so under-developed that they could not support the mission, leaving air transport as the only practicable way to supply China in anything resembling a timely fashion.

The first crews and aircraft to arrive from the USA were allocated to the 1^st Ferrying Group, and on 17 May reached at their base at the New Malir Cantonment near Karachi in north-west India. The group was activated in India in March without personnel or equipment and assigned to the operational control of the 10^th AAF over the objections of the commander of ATC who feared, not without foundation, that its aircraft and crews would be diverted into combat units. Small numbers of aircraft continued to arrive through October, the crews of these machines comprising airline pilots holding Air Corps Reserve commissions and called to active duty specifically for the India-China assignment, and navigators, engineers and radio operators from USAAF technical training schools.For the rest of 1942, the 62 C-47 aircraft of the 1^st Ferrying Group were the backbone of the airlift, flying both branches of the operation from Karachi until August, when it began a three-month relocation to Assam.

In the airlift’s first two months, the USAAF delivered just 700 tons of cargo and the CNC only 112 tons, and the tonnages fell in June and July, mostly as a result of the full onset of the summer monsoon. In July, the CNAC quadrupled its tonnage to 221 tons, but the 10^th AAF delivered only 85 tons of matériel and personnel into China.

On 17 June 1942, Haynes moved to China to became the bomber commander within the China Air Task Force, which was the 10^th AAF’s north-eastern appendage commanded by Brigadier General Claire L. Chennault and the precursor of the 14^th AAF. Scott was left in command for several days before he too was ordered to China to command the first US fighter group in the CATF. On 22 June Colonel Robert F. Tate succeeded Haynes, but was also in charge of the Trans-India Command in Karachi and remained in that capacity. Lieutenant Colonel Julian M. Joplin, acting at the direction of Naiden, effectively commanded the India-China operations until 18 August. Tate took actual command on 25 August, when Naiden returned to the USA, but like Naiden he delegated direction of airlift operations to Joplin. From 15 July 1942 the two branches of the India-China Ferry merged into the India-China Ferry Command within the 10^th AAF.

Right from the start, Tate was severely limited when the best pilots and 12 aircraft were sent to Egypt with Brereton on 26 June. Despite the use of the 1^st Ferrying Group, the build-up of the airlift grew only very slowly during the summer monsoon. Over-use of the small number of aircraft available, indifferent maintenance and a lack of spare parts combined for force many groundings until overhauls could be effected. In particular the lack of replacement tyres and engines held down operations even after eight of the C-47 aircraft earlier sent to the Middle East returned in August. For a short period of time engines intended for Republic P-43 Lancer fighters of the Chinese air force were adapted for C-47 use, but the supply of these engines was small.

Although three bases constructed by the British on tea plantations at Chabua, Mohanbari and Sookerating became operational in August 1942, and construction of a fourth began at Jorhat, none of these was as yet capable of all-weather operations. Nor were any of the airfields expected to be fully ready before November or December because of problems with unskilled labour and the non-arrival of the promised heavy construction equipment from the USA. Throughout the monsoon rains Dinjan remained the chief transport base. The poor results of the India-China Ferry to this point led to a proposal in Washington to reassign the operation of the airlift entirely to the CNAC, which would have had the effect of placing US military personnel in a combat area under foreign civilian control. Stilwell vigorously and successfully opposed the plan, and reinforced his position by insisting that the CNAC lease the C-53 aircraft and their crews to the USAAF to assure that they would carry only essential cargo and not undertake commercial operations.

The airlift suffered the first accidental loss of the aeroplane on 23 September, probably to icing, and after this the loss of transport aircraft increased sharply in number.

Protection of the aerial supply line became the 10^th AAF’s primary mission. When the summer monsoon ended, the Japanese were expected to attempt the severance of the last remaining connection to China, and although 10^th AAF’s CATF was adequate for the defence of the airlift’s eastern end in China, little had been done to create an anti-aircraft defence of the four airfields in Assam at the western end. Colonel Holme L. Sanders’s 51^st Fighter Group was nominally responsible for fighter protection, but two of its three squadrons had been stripped of their aircraft and personnel in July to equip the group’s third squadron and bring up to strength Colonel Robert L. Scott’s newly activated 23^rd Fighter Group, both in China with the CATF. The 51^st FG remained in Karachi as it waited for aircraft and personnel. Requests for more anti-aircraft guns, a weather squadron, and radio and land line communications equipment for the establishment of an early warning system were immediately approved, but remained unfulfilled for a variety of reasons.

The India Air Task Force, the 10^th AAF’s western combat force, was activated 3 October with nine squadrons, none of which was fully operational, and Haynes assumed command after promotion to brigadier general. The 51^st FG had been re-equipped with Curtiss P-40 fighters, but had trained pilots sufficient for only one squadron, which Haynes sent to Dinjan.

The long-anticipated air attack by the Japanese took place late in the afternoon of 25 October, when 100 bombers and fighters, bombing from 10,000 ft (3050 m) and strafing from 100 ft (30 m), achieved complete surprise. The only defence was provided by three P-40 fighters in the air on patrol, and six others which took off and gave pursuit. Dinjan and Chabua were heavily bombed, and nine transports and 20 fighters were destroyed or badly damaged by low-level strafing. On the following day Sookerating was strafed by 30 fighters, again without warning, but the damage was confined to a single storage building containing food and medical supplies. A third raid targeted Chabua on 28 October, but missed the airfield. Although the India Air Task Force had flown reconnaissance missions over the captured airfield at Myitkyina all through the summer, the Japanese had equipped their fighters with external fuel tanks and mounted the raids at longer range from Lashio or bases in southern Burma.

Haynes responded by moving the 51^st FG’s other squadron to Sookerating, while the CATF was ordered to launch a series of B-25 bomber attacks on Lashio. While Chennault complied, he did not believe that the Japanese strikes originated there and the rift between him and the 10^th AAF worsened. However, there were no more Japanese raids in 1942. In June 1943, following small, sporadic raids during the dry season, the entire fighter strength of the India Air Task Force, amounting to less than 100 P-40 aircraft, was organised as the Assam American Air Base Command (later the 5320^th Air Defense Wing, Provisional) for the specific task of protecting the Assam airfields.

The USAAF evaluated the airlift in October 1942 and as a result, the attitudes of the 10^th AAF’s senior officers with regard to the feasibility of the airlift operation were deemed to be 'defeatist'. The living conditions for both flight crew and ground personnel, especially at Dinjan, were described as 'by far the worst in the entire theater', with primitive quarters, poor sanitation, bad food and mess facilities, pervasive disease, and lack of recreation. Apathy became widespread and morale dropped to a 'dangerous point', with the feeling among the troops that as part of the 10^th AAF they were 'illegitimate children'.

On 13 October the Air Transport Command offered to take over the operation, and was ordered to do so eight days later, with effect from 1 December. The new command structure activated the India-China Wing ATC commanded by Colonel (later Brigadier General) Edward H. Alexander, Stilwell’s air officer. Alexander had been a founding member of ATC in 1941 as executive officer of the Ferrying Command. The India-China Wing reported directly to the ATC’s chief-of-staff in Washington, DC, Colonel (later Major General and ATC deputy commander) Cyrus R. Smith under the supervision of the Headquarters AAF, so ending the division of authority which had adversely affected the functioning of the India-China Ferry Command. The 1^st Ferrying Group returned to the ATC and was redesignated the 1^st Transport Group: its 76 C-47 aircraft were augmented in January 1943 by three Consolidated C-87 Liberator Express transport machines, a number increased to 11 in March and to a projected total of 50 by the end of the summer.

With the start of the heavy monsoon rains in March, the ATC operation was limited to the only all-weather base at Chabua (the base at Dinjan now being occupied by the CNAC and the 10^th AAF’s only P-40 fighter group), but there was a critical shortage of flight crews and it proved impossible to attain the ATC’s modest goal of 4,000 tons per month. Colonel Eugene H. Beebe’s 308^th Bombardment Group reached its base at Kunming on 31 March 1943 and began two months of reverse 'Hump' operations, flying round trips to India to build up the stocks of fuel, bombs, parts and other matériel it needed before starting to fly combat missions. Using kits developed by the South India Air Service Command Depot, it converted its B-24 bombers into fuel transports to accomplish the task. The 308^th BG used Chabua airfield, already crowded with more than 80 India-China Wing transport aircraft, and the airfield’s lightly constructed runway was soon giving way under the bombers' weight. Jorhat had stronger runways but its taxiways were still unpaved, making it unsuitable for four-engined aircraft. Both Sookerating nor Mohanbari were due to have strong concrete runways capable of handling all aircraft, but neither was yet paved and monsoon rains made them inoperable.

The first of 30 Curtiss C-46 Commando aircraft, an unproved cargo transport whose performance was superior to that of the C-47 in cargo capacity and ceiling, reached India on 21 April 1943 and during May the 22^nd Ferrying Group began operations with this type from the still uncompleted base at Jorhat, which had a concrete runway. In June, despite the fact that the British and later the US Army’s Services of Supply failed to complete construction of all-weather runways at Mohanbari and Sookerating, the 28^th, 29^th and 30^th Transport Groups were activated within an attempt to expand the C-46’s role to meet projected levels of tonnage. (The use of 'groups' and subordinate 'squadrons' to identify ATC units continued until 1 December 1943, when the command discontinued the group/squadron system and instead started to determine the size of its flying units within any wing by exact manning requirements for each base controlled by the wing, giving it the flexibility of moving men and aircraft around within the wing to meet mission requirements. After 1 December, units were identified by the station numbers of their bases.)

The severe crew shortage led to Alexander’s pleas for additional personnel. Project 7 was therefore established by the ATC at the end of June to fly nearly 2,000 men, 50 transport aircraft and 120 tons of matériel from Florida to India. Despite this, July’s tonnage was less than half of that planned. The airfields were nowhere near completion, nearly all of the new pilots had been single-engine instructor pilots, specialised maintenance personnel and equipment had been sent by ship, and the complexities of the new C-46 had now started to become evident. The great heat and torrential rains of the summer monsoon also made malign contributions toward the undermining of the ambitious goals. The long-delayed work on existing fields led Marshall to order Wheeler to have the Services of Supply complete the work by 1 July and issued a deadline of 1 September 1943 to have three additional fields ready for operations, but airfield construction problems were not overcome for several months.

At a meeting with General (later General of the Army) Henry H. Arnold, the commander of the USAAF, Chiang Kai-shek warned that the price of China’s co-operation with Stilwell for the reconquest of Burma was an air force, with 500 aircraft, and the airlifted delivery of 10,000 tons per month. In May 1943, at the 'Trident' second Washington conference, Roosevelt ordered the ATC to increase its monthly deliveries to China to 5,000 tons by July, 7,500 tons by August and 10,000 tons by September 1943. This came about as Marshall and Arnold despatched Major General George E. Stratemeyer, the chief of the air staff, on a special mission to observe India-China Wing operations and make recommendations. Similarly, Edward V. Rickenbacker, the USA’s highest-scoring fighter ace of World War I and currently head of Eastern Air Lines, flew the 'Hump' in a C-87 to reach China during his fact-finding mission to the Far East and the USSR. Both Stratemeyer and Rickenbacker found the performance of the India-China Wing to be deficient. While the wing was carrying more tonnage by virtue of having nearly 10 times as many aircraft as the CNAC (and half of those with a larger load capacity), the Chinese carrier was far more efficient in tonnage lifted per aeroplane by a factor of 2.5/1. The primary cause of ATC’s failure was the complete inadequacy of its airfield facilities, but other major factors were unsatisfactory performance by overwhelmed aircraft maintenance personnel, which resulted in the grounding of about 100 ATC aircraft every day, a predominance of inexperienced pilots, and a shortage of radio and navigation aids in ATC transports. Rickenbacker and the 10^th AAF’s commander, Major General Clayton L. Bissell, recommended the the airlift operation be returned to theatre command, but Stratemeyer disagreed, as did Major General Howard C. Davidson, who was about to replace Bissell as 10^th AAF commander, and had made an inspection tour of his own in June.

Frustration about the India-China Wing’s failure to meet the 'Trident' goals caused Arnold in September 1943 to dispatch another inspection team to India, this being led by the ATC commander Major General Harold L. George. Accompanying George was Colonel Thomas O. Hardin, a forceful former airline executive who had already been overseas for a year as head of the ATC’s Central African Sector. On 16 September, George immediately reassigned Hardin to command the new Eastern Sector of the India-China Wing with instructions to reinvigorate India-China operations. Alexander was replaced in command of the India-China Wing by Brigadier General Earl S. Hoag on 15 October. George also instituted the 'Fireball' weekly C-87 express flight by the 26^th Transport Group to deliver critical spare parts for the transport aircraft from the Air Service Command Depot at Fairfield, Ohio, to the ATC service depot at Agra, India.

Japanese fighters based in central Burma began to challenge the transport route near Sumprabum at the end of the summer monsoon. On 13 October, a large number of fighters assisted by ground observers evaded US fighter patrols and shot down single C-46, C-87 and CNAC transport aircraft, and damaged three others. US fighter patrols were doubled, but similar interceptions on 20, 23 and 27 October resulted in the loss of five more C-46 aircraft. On the last of the interceptions, a formation of B-24 bombers on a reverse 'Hump' mission was mistaken for a C-87 mission and claimed eight fighters shot down. The 10^th AAF immediately began attacks on Japanese airfields (Myitkyina was attacked 14 times before the end of the year) and the India-China Wing moved its route to Kunming even farther to the north. Only two more C-46 aircraft were shot down during the remainder of 1943, both in December.

Some 20 Japanese bombers escorted by 25 fighters bombed the Assam airfields on 13 December 1943 after several days of probing the early warning system had not presaged an attack. Despite an increase in fighter patrols and the issue of an alarm, the defenders had only a 12-minute warning. US fighters were unable to climb to the 18,045-ft (5500-m) altitude of the bombers in time to prevent the bombing, but only slight damage resulted. The raiding force was pursued and attacked, then ran head-on into fighter patrols returning from northern Burma. Serious losses apparently convinced the Japanese not to repeat the attacks.

Hardin altered operations by introducing night missions and refusing to cancel scheduled flights because of adverse weather or threat of interception. Although losses to accidents and Japanese action increased, and replacements for the high number of C-46 aircraft lost ceased entirely for two months, the tonnage delivered increased sharply. The operation finally surpassed its objective in December, with more than 12,500 tons delivered to Kunming when new C-46 aircraft loaded with much-needed C-46 spare parts began to reach India in significant numbers. By the end of 1943, Hardin had 142 aircraft (93 C-46, 24 C-87 and 25 C-47 machines) available.

In February 1944 the first few Douglas C-54 Skymaster four-engined transport aircraft reached India. With a maximum-load ceiling of only 12,000 ft (3660 m), the C-54 was not able to overfly the high 'Hump', Japanese fighters blocked use of eastbound routes at lower altitudes, and the C-54 machines were limited for a time to freight movement within India or flights between the CBI and the continental USA.

Hardin was elevated to command of the India-Chine Wing on 21 March 1944 when Hoag was transferred to lead the ATC’s European Wing. One month later, to give Hardin closer personal contact with his growing number of air bases, the headquarters of the India-China Wing was relocated from New Delhi to Rishra, to the north of Calcutta in north-eastern India. Here Stratemeyer, now a lieutenant general and commander of all USAAF forces in the CBI, established Hastings Army Air Base as the headquarters of the Army Air Forces India-Burma Theater, using a converted 8.5-acre (34,000 m2) mill building to house his headquarters as well as those of the CBI Air Service Command and the India-China Wing. Under Hardin’s leadership, tonnages increased but so did expectations and frustrations, and both morale and safety concerns continued to plague the operation. In the first 54 days of 1944, 47 transport aircraft were lost: this was one transport for every 218 flights and 1.968 aircraft lost per 1,000 flying hours. One life was being lost for every 162 trips flown, or 340 tons delivered.

In June 1944, after the capture of the Japanese fighter base at Myitkyina and at the behest of Brigadier General William H. Tunner, commander of the ATC’s Ferrying Division, Colonel Andrew B. Cannon was assigned to command the Assam Wing on its activation in the following month. Tunner, who was to become the commander of the ATC’s India-China Division on 4 September in succession to Hardin, anticipated that the end of the fighter threat would see a massive influx of C-54 aircraft into the India-China operation. Like Haynes, Alexander and Tunner, Cannon had been a pioneer in the Air Transport Command, where as a protégé of Tunner he was base commander of Long Beach Army Air Field, headquarters of Tunner’s ATC Ferrying Division, and commanding officer of the 6^th Ferrying Group. On 1 July, ATC reorganised its nine wings worldwide into air divisions, and sectors into wings. The India-China Wing this became the India-China Division, while the Eastern Sector, carrying out the India-China airlift, was redesignated as the Assam Wing, and the Western Sector support organisation became the India Wing. The India-China Division had an operational training unit at Gaya, and used the service depots of the China-Burma-India Air Service Command at Panagarh, Agra and Bangalore.

The ATC ended its use of station numbers as unit identifiers on 1 August 1944 and formed numbered AAF Base Units. These collectively identified all permanent party organisations, including flying units, at any particular non-combat base, and the flying units were generally denoted as lettered squadrons within the base unit. The various organisational changes affecting the India-China airlift between 1942 and 1944 can be exemplified by the changes in designation of a single unit: the 1^st Ferrying Group at Chabua under the 10^th AA became the 1^st Transport Group on 1 December 1942 to denote that it was an ATC unit; Station No. 6 on 1 December 1943 when for flexibility the ATC no longer fielded groups or squadrons, and finally the 1333^rd AAF Base Unit (Foreign Transport Station) on 1 August 1944 in conformance with service-wide USAAF policy.

Hardin returned to the USA after two years of overseas service, and command of the India-China Division then passed to Tunner, who assumed command on 4 September 1944 with orders to increase the tonnage delivered, reduce the numbers of lives and aircraft lost in accidents, and improve morale in the India-China Division. Making use of a 'big business' approach, Tunner and his staff revitalised the operation, improved morale and cut the aircraft loss ratio by two while doubling the tonnage of cargo delivered.

Tunner made extensive use of more than 47,000 Assamese labourers and had at least one elephant to lift 55-gal (208-litre) fuel drums into aircraft. A daily 'Trojan' direct flight flown by selected C-54 crews carried a minimum of five tons of highest-priority matériel or passengers between Calcutta and Kunming, then brought back critically wounded patients or aircraft engines needing overhaul. Tunner assigned each base both daily and monthly tonnage quotas to move over the 'Hump' based on the type of aircraft it operated and its distance from the 'Chinaside' destination airfields. Tunner also reinstituted military standards of dress, drill and behaviour, which had perceived as slack in the previous year.

In Tunner’s first month of command, although the India-China Division delivered 22,314 tons to China, it still incurred an accident rate of 0.682 per 1,000 flight hours. By January 1945, the division had 249 aircraft and 17,000 personnel. It delivered more than 44,000 tons of cargo and passengers to China during that month at an aircraft availability rate of 75%, but also suffered 23 fatal crashes and 36 crewmen killed. On 6 January a powerful winter storm blasted across the Himalayan mountains from west to east, increasing the time of westbound trips by one hour, and caused 14 CNAC and ATC transports to be lost or written off, with 42 crewmen missing, which was the single greatest one-day loss of the 'Hump' operation. The accident toll increased in the two months that followed, with 69 aircraft lost and 95 crewmen killed.

To reduce losses resulting from mechanical failure, in February 1945 Tunner introduced the Production Line Maintenance programme, in which each aeroplane due for 50- or 200-hour maintenance was towed through five to seven maintenance stations, depending on whether or not an engine change was required. Each station had a fresh maintenance crew trained for a specific service task, and the process that took nearly a full 24-hour day per aircraft to complete. Each base specialised in only one type of aeroplane to simplify the process. Despite initial resistance, the PLM programme was implemented throughout the division, and proved very successful.

Tunner also adopted two measures to lower the number of mishaps in the air as a result of inexperience and crew fatigue. For the first, Tunner appointed Lieutenant Colonel Robert D. Forman as division training officer to oversee both stringent training and a flying safety programme supervised by Captain Arthur Norden. From 15 March 1945 the programme was intensified after Major John J. Murdock had taken over as division flying safety officer. Tunner also altered the personnel rotation policy of the India-China Division, which he saw as a major contributor to crew fatigue. Before Tunner took command, pilot tours were set at 650 flight hours over the 'Hump', which many pilots abused by flying daily in order to be rotated back to the USA in as few as four months. As a result the division flight surgeon reported that half of all crewmen suffered from operational fatigue. Effective 1 March 1945, Tunner increased the number of flight hours required to 750, and dictated that all personnel had to be in the theatre for 12 months before being considered for rotation, and this effectively discouraged over-scheduling.

Under Tunner’s leadership, the India-China Division expanded to four wings in December 1944. The expansion was necessary to control the multiplicity of AAF Base Units created as more airfields became operational. In addition to the Assam and India Wings, the India-China Division added the Bengal Wing, headquartered at Tezgaon, to control C-54 operations, and the China Wing at Kunming. Tunner relocated veteran commanders to provide leadership to the new wings: Cannon switched to the Bengal Wing, while Colonel Richard F. Bromiley moved from the India Wing to the China Wing. Colonel George D. Campbell succeeded to command of the Assam Wing.

Both the accident rate and the number of accidents decreased notably as a result of these measures. The exception was the figures of the C-87 and C-109 transport versions of the Liberator bomber, which remained 500% higher than those of the C-54. Tunner called for the replacement of the two Liberator variants by C-54 aircraft, and plans were laid for the increase of the C-54 force to 272 by October 1945 and 540 by April 1946. With a fleet of 410 C-46 aircraft augmenting the India-China Division, the over-the-'Hump' tonnage was predicted to become more than 86,000 tons per month. A shortage of C-54 engines hampered the plan, which was modified to have a quarter of the force always in a pipeline between India and Florida for engine changes, carrying cargo and passengers as they travelled in each direction. The modified plan was approved in April 1945 and Morrison Field, Florida, was chosen for the maintenance. However, C-54 aircraft sent there remained at the field for periods five times the seven days originally estimated for each turnaround.

In July 1945, the last full month of operations, 662 aircraft of the India-China airlift delivered 71,042 tons, the India-China Division’s maximum monthly tonnage. Of these 662 aircraft, 332 were India-China Division transports, but 261 were combat aircraft from army air force units temporarily assigned to the airlift. An average of 332 flights to China was scheduled daily. The India-China Division had 34,000 USAAF personnel, and including civilians of all nationalities employed in India, Burma and China, 84,000 persons overall. It boasted an aircraft availability rate of more than 85%. The India-China Division suffered 23 major accidents in July, with 37 crewmen killed, but the 'Hump' accident rate declined to 0.358 aircraft per 1,000 flying hours in July (one-fifth of what it had been in January 1944) and 0.239 in August.

On 1 August 1945 the India-China Division organised its largest mission of the airlift. The division flew 1,118 round-trip sorties, averaging two per aeroplane, and one C-54 logged three round trips in 22 hours 15 minutes of operations. Some 5,327 tons were delivered in one day without fatality, and there were no major accidents. C-87 and C-109 aircraft carried 15% of the tonnage without mishap. Before the end of the month, nearly 50,000 more tons were delivered. Eight major accidents resulted in only 11 deaths, at a rate of one death for every 2,925 trips (1/18^th of what it had been in January 1944). The major accident rate of only 0.18 aircraft lost per 1,000 flight hours was one-third of what it had been when Tunner took command, and one-eighth of that of January 1944.

Tunner remained in command of the division until 10 November 1945, and then the deputy commander, Brigadier General Charles W. Lawrence, commanded the division for the five days before it was disbanded on 15 November 1945.

The first significant diversion of India-China Wing resources to operations other than the 'Hump' airlift began in February 1944. The Japanese 'Ha' offensive in the Arakan western coastal region of Burma, followed by the 'U' offensive against Imphal in March and April, resulted in the need to aid the British forces that Hardin estimated reduced 'Hump' deliveries by 1,200 tons. The India-China Wing also had a stake in resistance to the offensive because the threat to Imphal also imperilled the Assam-Bengal railway along which not just 'Hump' cargo but fuel for the airlift passed. The crisis occasioned by the Japanese attack on Imphal led Admiral the Louis Mountbatten, commander-in-chief of the South-East Asia Command, to request 38 C-47 aircraft to aid in the reinforcement of Imphal. While Mountbatten had no authority to divert aircraft from 'Hump' operations, his request was supported by two of the principal US commanders in the theatre, namely Major General Daniel I. Sultan, deputy commander of the CBI Theater, and Stratemeyer, who in addition to all his other duties commanded SEAC’s Eastern Air Command and was thus, for all practical purposes, Mountbatten’s air commander. After the request had been approved, the India-China Wing provided 25 C-46 aircraft as the equivalent of 38 C-47 machines, and these were attached to the EAC Troop Carrier Command for the support of the British and were used to fly the personnel and light equipment of Major General G. C. Evans’s Indian 5^th Division to Imphal and Dimapur, where it arrived in time to thwart the Japanese offensive.

In the following month, to reinforce Stilwell’s 'Plan X' offensive into Burma, the India-China Wing flew 18,000 Chinese troops to the west across the 'Hump' to Sookerating, which resulted in a net reduction to the India-China effort of at least 1,500 tons. However, the capture in May 1944 of Myitkyina airfield by US and Chinese troops of Stilwell’s command deprived the Japanese of their principal fighter airfield from which to threaten Allied aircraft flying over the 'Hump'. The field immediately became an emergency landing strip for Allied aircraft even though fighting continued in Myitkyina town until August 1944. The India-China Division continued its contribution to this success by flying a regiment-sized force of combat engineers and their support, including heavy equipment, from southern India for airfield construction. The capture of Myitkyina allowed C-54 aircraft, whose fully-laden ceiling limitations precluded flying Route Able (the 'High Hump'), to make regular use of a second and more direct route, designated Route Baker but unofficially dubbed the 'Low Hump'.

In October 1944, after Tunner took command of the India-China Division, larger numbers of C-54 aircraft, sometimes escorted by Allied fighters based at Myitkyina, greatly increased tonnage levels flown to China from India. The C-54, which could carry 10 tons (five times the cargo load of the C-47 and twice that of the C-46), replaced both twin-engined transports as the primary lifter of the operation. The expansion of bases resulted in the establishment of the eastbound Routes Easy, Fox, Love, Nan, and Oboe, and also the westbound Route King.

From April 1944 to January 1945, the India-China Division also supported 'Matterhorn', the Boeing B-29 Superfortress strategic bombing campaign against Japan from forward bases around Chengtu in central China. Arnold had originally envisaged that 'Matterhorn' units would be self-sustaining, bringing in their own fuel in hundreds of C-109 machines and other matériel using B-29 and 20 C-87 machines as their own air transport service. The concept proved to be flawed right from the start after the planned 300-bomber force was reduced to a single combat wing of 150 bombers before it left the USA. B-29 bombers of Brigadier General LaVern G. Saunders’s (from 29 August Major General Curtis E. LeMay’s) XX Bomber Command, stripped of guns and other equipment and fitted with four fuel tanks in their bomb bays, were used as fuel tankers, while tactical aircraft carried other supplies, including bombs. This was inadequate for the task of delivering sufficient matériel over the 'Hump' from their permanent bases around Calcutta in India to allow the start of effective operational missions. The XX Bomber Command therefore turned to the India-China Division for additional support after the target date for the start of its missions had been postponed repeatedly.

The ATC’s North African Wing had already provided an interim level of support by transporting 250 spare B-29 engines to the CBI in April and May 1944, using 25 C-54 aircraft on a 6,200-mile (9975-km) shuttle route from the port of Casablanca in French North-West Africa to Calcutta. This 'Crescent Blend' effort lasted until three 'Moby Dick' special mission C-46 squadrons were created early in 1944 to fly supply operations for the XX Bomber Command. These the 1^st, 2^nd and 3^rd Air Transport Squadrons (Mobile) were each intended as a self-contained unit of 20 C-46 aircraft, flight crews, maintenance and engineering specialists, and a full complement of station operation personnel, although when first committed the service elements had not yet been integrated. The three squadrons reached the CBI in June 1944, when the 1^st and 2^nd MATS were based at Kalaikunda in West Bengal, taking over the 'Crescent Blend' shuttle and delivering more than 100 spare engines per month, while the 3^rd MATS was sent forward to the India-China Division base at Kunming to augment the 'Hump' airlift.

Of the 42,000 tons of matériel delivered before the XX Bomber Command had abandoned its China bases in the face of the Japanese 'Ichi' offensive and return to India, the India-China Division carried almost two-thirds. During the last three months of its bombing operations from China, the XX Bomber Command quickly ended the use of its B-29 bombers to carry cargo, and the India-China Division supplied all of the XX Bomber Command’s matériel except bombs, which B-29 bombers carried over the 'Hump'. Lieutenant Colonel Robert S. McNamara created a statistical control section to create the required adjustable schedules.

Unfortunately for its, the XX Bomber Command arrived in the theatre just as the Japanese were beginning a major offensive in eastern China to open a corridor for overland lines of communication to its forces in Indo-China, seize the airfields of Chennault’s 14^th AAF located in that corridor, and if at all possible knock China out of the war. The load allocations which the India-China Division had to commit to the XX Bomber Command led to mutual recriminations between the XX Bomber Command, the India-China Division and Chennault, from whom most of the altered allocation tonnage was taken, with each blaming the others for the operational problems which resulted. The Japanese offensive continued apparently inexorably all summer and into the autumn, threatening the capability if not the existence of the 14^th AAF. Relations were never entirely smoothed with Chennault, but workable compromises were eventually fashioned by Stratemeyer, Hardin and Tunner to accomplish the tasks necessary to keep the 14^th AAF in being and operational. Supplying 'Matterhorn' during the concurrent crisis did have the positive effect of increasing the resources and effort committed to the airlift, and recognition by all involved that the India-China Division was the only formation which could handle the logistics efficiently.

When the ATC was reorganised on 1 August, the MATS squadrons maintained a separate identity from the newly created AAF Base Units, but each flew hundreds of 'Hump' missions, delivering aviation fuel and engines. Because India-China operations were of extraordinary length from Kalaikunda, which necessitated an intermediate stop at Jorhat, the two squadrons were transferred to the India-China Division when the XX Bomber Command began planning the reduction of its operations in November 1944. On 30 October the 2^nd MATS moved to Dergaon, East Bengal, and later to Luliang, China, where it was disbanded in June 1945 and became Squadron B, 1343^rd AAF Base Unit.

As the C-46 and C-47 aircraft which landed in China were temporarily beyond ATC control, they were constantly diverted for local emergencies by Chennault’s 14^th AAF and Lieutenant General Albert C. Wedemeyer’s China Theater forces, disrupting the flight crew rest and aircraft maintenance schedules which had been instituted to maintain delivery tonnages. To alleviate the situation and also to provide the additional support needed by the combat forces, 50 C-47 and 20 C-46 aircraft were permanently based in China after October 1944 for internal movement of cargo and to assist the India-China airlift when gaps in local scheduling permitted. Most of the remaining C-47 machines were eventually sent to bases in Burma and continued India-China missions over the lower routes, and proved their continuing utility by playing prominent roles in various support missions within China in 1944 and 1945.

Between 5 December 1944 and 5 January 1945, C-46 aircraft and their crews were attached to the 10^th AAF to augment the 'Grubworm' relocation of Major General Long Tian-wu’s Chinese New 14^th Division and Major General Shan Yu-feng’s New 22^nd Division of Lieutenant General Sun Li-jen’s Chinese Army in India (New 1^st Army), from their reserve positions on the Stilwell Road near Myitkyina, to bases around Kunming. Chiang and Wedemeyer proposed to the Combined Chiefs-of-Staff, over the objections of Mountbatten, to relocate the divisions to counter a Japanese offensive to capture the Kunming airfields. The operation was approved with the proviso that it was not to strain the 10^th AAF’s extensive air transport system supplying Allied ground operations in Burma. The India-China Division provided the C-46 aircraft of the mobile air transport squadrons and all of its China Wing C-47 aircraft to provide the necessary augmentation.

The 2^nd ATS moved in entirety from its base at Dergaon to Luliang Field, China, completing the deployment by 13 December. The 1^st ATS operated from Ledo, and the India-China Division’s 1348^th AAF Base Unit at Myitkyina South airfield co-ordinated the entire operation and provided the staging base for refuelling all the transport aircraft. The C-46 force moved the New 14^th Division from five airfields in Burma, including a field at Nansin whose construction was completed on 4 December: here take-offs were subject to artillery and sniper fire. The 1348^th Base Unit scheduled operations 24 hours per day and in bad weather, although the operation was suspended between 16 and 22 December when the situation in China seemed to have improved. Of the six collection airfields, only Myitkyina South was capable of night operations, and C-47 troop carriers were used to shuttle troops there during the day for India-China Division aircraft to fly over the 'Hump' at night.

As they were familiar with the Burma airfields, the mobile air transport squadrons were selected to fly the operation. Showing unusual flexibility in planning, the 1348^th Base Unit quartered incoming troops near airfields, supplied them, monitored the availability of aircraft and crews, divided the troops into planeloads, and kept Chinese units and their matériel intact. Briefings and fuellings were conducted at Myitkyina South, the aircraft transited to their collection fields and loaded, and then flew back to Myitkyina South for a final refueling before flying on to China. The 1348^th Base Unit control tower performed all air traffic control of aircraft to and from China.

'Grubworm' transported 25,009 Chinese troops, 396 Americans, 1,596 draft animals, 42 Jeeps and 144 pieces of artillery in 24 days of flying. India-China Division crews provided 597 of the operation’s 1,328 sorties, and moved more than 14,000 of the troops involved. Although three C-47 aircraft were lost during the operation, the India-China Division suffered no losses. When the Japanese offensive shifted to seize the 14^th AAF’s bases at Suichwan and Kanchow, the 2^nd ATS evacuated the bases on 22 January.

Between March and May 1945, the India-China Division carried the first US combat troops into China when it redeployed the two US regiments of the 'Mars' Task Force from Burma. In April, 50 C-47 and 30 C-46 aircraft of the India-China Division undertook 'Rooster' to transport both divisions of Lieutenant General Liao Yao-xiang’s Chinese New 6^th Army from Kunming, where they had been delivered by 'Grubworm', to Chihkiang in the western end of the Hsiang river valley to reinforce the defence of the 14^th AAF base there. The India-China Division flew 1,648 sorties, delivering 25,136 troops, 2,178 horses and 1,565 tons of matériel for a total of 5,523 tons. Over the same period 369 tons of aviation fuel were also carried to Chihkiang for the 14^th AAF.

In overall terms, the initial task facing the 10^th AAF in the creation of the 'Hump' airlift was daunting in the extreme, and served to emphasise all that the USAAF lacked in April 1942: no units tasked for moving cargo, no experience in organised airlift by the USAAF and the US Army Air Corps out of which it had been created, and no airfields for basing units. In addition, flying in the region was made more difficult by a lack of reliable charts, an absence of radio navigation aids, and a dearth of weather data.

In 1942 Chiang Kai-shek insisted that at least 7,500 tons per month were needed to keep his field divisions in operation, but this figure proved unattainable for the first 15 months of the 'Hump' airlift, and the figure was exceeded for the first time only in August 1943, by which time the objective had been increased to 10,000 tons er month. Ultimately the monthly requirement exceeded 50,000 tons. An airlift of unprecedented scale slowly began to take shape, however. Construction of four new bases was begun in 1942, and by 1944 the operation flew from six all-weather airfields in Assam. During July 1945, the air corridor from India began at the 13 airfields along the North-East Indian Railways section of the Brahmaputra river valley as seven in Assam, four in the Bengal valley and two near Calcutta, and terminated at six 'Chinaside' airfields around Kunming.

Up to July 1944 the flight corridor for the 'Hump' airlift was 50 miles (80 km) wide and was characterised by a highly restricted vertical clearance. As bases expanded and the 'Low Hump' route came into use, the corridor widened to 200 miles (320 km) and 25 charted routes, with a vertical clearance of 10,000 to 25,000 ft (3050 to 7620 m) in the south, permitting highly congested but controlled operations at all hours.

A critical problem was the provision of a cargo aeroplane able to carry a heavy payload at the high altitudes required, and three types were tried before the opening of a 'Low Hump' route permitted the use of the C-54: these were the twin-engined C-47 and its variants, twin-engined C-46, and related four-engined C-87 and C-109.

Initially, the India-China airlift was flown using the DC-3 and its C-47 and C-53 military versions, and the earlier DC-2 and its C-39 military version. However, the design of the DC-2 and DC-3 meant that the fuselage was so high off the ground that loading from most truck beds was difficult, the door was narrow, and the floor too weak to support heavy cargo. Although the C-47 had a wider door and a reinforced floor, it still required specialised loading equipment for much of the cargo needed in China, and had a limited payload capability. Moreover, the Douglas transports were not suited to high-altitude operation with heavy payloads, and could not normally reach an altitude sufficient to clear the mountainous terrain, forcing the aircraft to adopt a highly dangerous route through the maze-like Himalayan passes.

The January 1943 advent of the C-87 Liberator Express, adapted from the B-24D heavy bomber, boosted payload capability, and the new type’s good altitude capability enabled it to overfly the lower mountains, reaching up to 16,000 ft (4875 m) without having to resort to the passes, but the type had a high accident rate and was unsuited to the airfields then in use. Despite its four engines, the C-86 climbed poorly with heavy loads, and often crashed on take-off if an engine failed. Because of its high-aspect-ratio wing, it also had a tendency to spin out of control when encountering even mild icing conditions over the mountains.

The other Liberator transport variant, the C-109, was based on B-24J or B-24L conversion and intended for the carriage of fuel. All combat equipment was removed and eight flexible bag fuel tanks, with a capacity of 2,900 US gal (10980 litres), were installed inside the fuselage. Some 70 of this type were initially planned to fly the 'Hump' with the XX Bomber Command, beginning in September 1944, but most of the 218 C-109 conversions eventually served in the CBI for the ATC after B-29 operations had been shifted from China back to India. At least 80 of these aircraft were involved in major accidents between September 1944 and August 1945. Like the C-87, the C-109 was not popular with its crews as it was difficult to land when fully loaded, particularly at airfields such as those round Kunming at altitudes above 6,000 ft (1830 m), and often suffered from unstable flight characteristics when all eight fuel cargo tanks were full. The crash landing of a loaded C-109 inevitably resulted in an explosion and crew fatalities.

The C-46 Commando began to fly 'Hump' missions in May 1943. A large twin-engined type able to fly faster and higher than any previous medium-range cargo aeroplane, the C-46 could carry heavier loads than either the C-47 or the C-87, but was 2.5 times more expensive to build than the C-47.The advent of the C-46 meant a major increase in airlift tonnage, surpassing objectives with 12,594 tons in December 1943. Loads continued to increase throughout 1944 and 1945, reaching an all-time maximum tonnage in July 1945. The C-46’s performance was improved when camouflage paint, standard on all USAAF aircraft until February 1944, was removed to reduce weight and provide an extra 6 mph (10 km/h) of speed. The C-46 rapidly became the medium-range workhorse of the 'Hump' airlift, but was prone to mechanical failures,(especially engine failures, When it first arrived in the theatre, the C-46 also required that additional training be given to inexperienced crews, and a transition school was established that drained the airlift of 10 aircraft and crews. Moreover, spare parts were in such scarce supply until the autumn of 1943 that 26 of the first 68 C-46 to reach India were unserviceable.

Operations over the 'Hump' proved to be an extremely hazardous undertaking for Allied flight crews. The air route wound its way into the high mountains and deep gorges between north Burma and west China, where violent turbulence, 125 to 200 mph (320 km/h) winds,[21][102] icing, and inclement weather conditions were a regular occurrence. Lack of suitable navigational equipment, radio beacons, and inadequate numbers of trained personnel (there were never enough navigators for all the groups) continually affected airlift operations.

In the first year of the airlift, inexperienced officers of the Services of Supply frequently ordered aircraft to be loaded until they were 'about full', ignorant of weight limitations and centre of gravity location, while most pilots were reservists recently called up from airlines with little military transport experience and accustomed to civilian safety standards. As the airlift grew in size and scope in 1943, demands of tactical units and the failure of airline-conducted ATC training programmes to produce sufficient numbers of multi-engined pilots limited nearly all reinforcement pilots to those just out of flight school or single-engine rated pilots from training fields with only little instrument flying time. In December 1942, one-third of the 102 technical sergeant pilot training graduates of one class at Lubbock Field were sent straight to India to fly the 'Hump' as replacement co-pilots. The level of collective inexperience required the India-China Wing to create an in-theatre operational training unit near Karachi to qualify new arrivals, removing 16 experienced pilots and eight to 10 aircraft from the airlift. While accustomed to flying a variety of aircraft, Chinese pilots also lacked adequate instrument flying experience, and most were unfamiliar with the large US transport aircraft used in the airlift. Not until 1944, when the ATC recruited high-hour civilian flight instructors released by the USAAF in it its reduction of the pilot training programme, and the 3^rd OTU at Reno AAF, Nevada, qualified larger numbers of C-46 crews, were highly qualified replacements more readily available for the airlift.

Even so, US and Chinese pilots often flew daily on round-trip flights by day and night. Some exhausted crews flew as many as three round-trips per day, particularly during the Hardin rotation policy. Mechanics serviced the aircraft in the open, using tarpaulins to cover the engines during the frequent downpours, and suffered burns to exposed flesh from sun-heated bare metal. There were insufficient mechanics and spare parts during the first two years of operations, and maintenance and engine overhaul were often deferred. Many overloaded aircraft crashed on take-off after losing an engine or otherwise encountering mechanical trouble. AS a result of the isolation of the area and the low priority allocated to the CBI theatre, parts and supplies to keep aircraft operational were in short supply until 'Fireball', and flight crews were often sent into the Himalayan foothills to cannibalise aircraft parts from the numerous crash sites. At times, monthly aircraft losses totalled 50% of all aircraft then in service along the route.

In addition to losses from weather and mechanical failure, the unarmed and unescorted transport aircraft flying the 'Hump' route were occasionally attacked by Japanese fighters, and some C-87 pilots added two 0.5-in (12.7-mm) fixed forward-firing machine guns below the fuselage in front of the cargo doors of their aircraft, though there is no documented evidence of the use of such armament.

The large number of losses resulted in the formation at Jorhat in July 1943 of one of the first search and rescue organisations, nicknamed 'Blackie’s Gang'. A former test pilot and a 'Hump' veteran, Captain John L. 'Blackie' Porter directed the unit using C-47 aircraft borrowed from airlift units and crewed by a dozen former barnstorming pilots and enlisted personnel armed with sub-machine guns and hand grenades. 'Blackie’s Gang' accounted for almost every crewman recovered in 1943. The unit moved to Chabua on 25 October, was given official status and was allotted two C-47 and several Stinson L-5 Sentinel liaison aircraft with which to rescue downed crews. Porter recruited volunteer medical personnel to parachute into crash sites to aid injured crewmen. Late in November Porter added two B-25 Mitchell machines to his small fleet, these being among aircraft which had been consigned to a salvage field. Porter was killed in action on 10 December 1943, when his B-25 was set on fire by Japanese fighters during a search mission and crashed on the Indian border while trying to return to base.

When he took command of the India-China Division, Tunner was not satisfied with the existing search-and-rescue arrangement. He appointed the operations officer at Mohanbari, former 'Hump' pilot Major Donald C. Pricer, to establish an efficient search and rescue organisation. Pricer’s 90 men of the 1352^nd AAF Base Unit (Search and Rescue) at Mohanbari used four B-25, one C-47, and one L-5 aircraft, each painted yellow overall with blue wing bands for easy identification, to conduct the search missions. Pricer also charted all known crash sites to eliminate checking previous wrecks, and on occasion called upon a Sikorsky YR-4 helicopter based at Myitkyina to assist in rescue missions.

ATC operations accounted for 685,304 tons of cargo carried to the east during hostilities, including 392,362 tons of fuel and oil, with nearly 60% of that total delivered in 1945. ATC aircraft made 156,977 eastbound flights between 1 December 1943 and 31 August 1945, losing 373 aircraft in the process. Though supplemented by the opening of the Ledo Road network in January 1945 and by the recapture of Rangoon, the airlift’s total tonnage of 650,000 net tons far exceeded the 147,000 tons transported along the Ledo Road. As well as cargo, 33,400 persons were transported, in one or both directions.

The CNAC’s crews made a key contribution to the 'Hump' operations. Between 1942 and 1945 the Chinese received 100 US transport aircraft in the form of 77 C-47 and 23 C-46 machines. Of the eventual 776,532 tons transported over the 'Hump', CNAC pilots accounted for 75,000 tons, about 12% of the total.

The 'Hump' airlift continued beyond the end of the war. The final missions of the India-China Division, flown after most of its attached organisations had departed, were the transporting of 47,000 US personnel westbound over the 'Hump' from China to Karachi for repatriation to the USA.

The maximum aircraft strength of the India-China Division on 31 July 1945 was 640 aircraft in the form of 230 C-46, 167 C-47, 132 C-54, 67 C-87/C-109, 33 B-25, 10 L-5 and one B-24 machines. Of the aircraft used in the 'Hump' airlift between 1942 and 1945, 594 were lost. At least 468 US and 41 CNAC aircraft were known lost from all causes, with 1,314 crewmen and passengers killed. In addition, 81 more aircraft were never accounted for, with their 345 personnel listed as missing. Another 1,200 personnel had been rescued or walked back to base on their own.

The final summary of logged flying time in the airlift totalled 1.5 million hours, and the India-China ferrying operation was the largest and most extended strategic air bridge (in volume of cargo airlifted) in aviation history until exceeded in 1949 by the Berlin airlift.