The wartime RCAF consisted of three main parts, two of which were in Canada. The British Commonwealth Air Training Plan the other the Home War Establishment - which was to deploy thirty-seven squadrons for coastal defense, protection of shipping, air defense and other duties in the western hemisphere. The third with its headquarters in London, England the Overseas War Establishment. At the end of the war it had forty-eight squadrons serving with the Royal Air Force in Western Europe, the Mediterranean and the Far East.

  On the first of January 1944 the RCAF reached its peak wartime strength of 215,200 all ranks (including 15,153) women, 104,000 were in the British Commonwealth Air Training Plan, 64,928 were serving at home and 46,272 were serving overseas. There were 78 squadrons in service: 35 overseas, 43 at home (of which six had been ordered overseas).