'BT' (iii) was the designation of Allied troopship convoys (together with a numerical suffix) plying the route between Australia and USA, and as such reciprocals of the 'TB' (i) series (January 1942/June 1943).

The first of the series was BT.200 of 23 January/26 February 1942 from New York to Melbourne with the 5,014-ton ex-Italian Argentina, 10,021-ton US Cristobal, 7,997-ton US J. W. McAndrew, 16,552-ton US John Ericsson, 9,135-ton US Santa Elena, 9,135-ton US Santa Rosa, and 11,250-ton US Thomas H. Barry. The last was BT.203 of 3/14 June 1943 from Bora Bora to Brisbane with the 20,614-ton US Brazil, 12,097-ton US Henry Gibbons, 11,250-ton US Thomas H. Barry, and 20,183-ton US Uruguay.