This was a British programme of special air mail flights operated by de Havilland Mosquito aircraft from the UK to the USSR, Italy and Egypt to carry diplomatic and military communications during 'Tolstoy', otherwise the 4th Moscow Conference (9/23 October 1944).
'Frugal' was undertaken by aircraft of No. 544 Squadron to Ramenskoye in the USSR via Memel, a journey which took an average of 6 hours 30 minutes. Vnukovo/Moscow later became the Soviet end of the service. Some 27 flights were made in 14 days, these carrying mail between Northolt and Moscow during the 4th Moscow Conference, the average speeds from take-off to landing being 314 mph (505 km/h) on the eastward trip and 300 mph (483 km/h) on the westward trip. On his return from the conference, Prime Minister Winston Churchill sent a message thanking the squadron for the punctuality of the service.
The flights were not without incident: on one trip a Mosquito encountered four German fighters (three piston-engined aircraft and one Messerschmitt Me 262 turbojet-engined fighter), and on another trip a Mosquito was intercepted by a Messerschmitt Me 163 rocket-powered interceptor near Dortmund, but escaped.
'Frugal' also involved mail flights to Cairo and Naples.