Veterans Affairs Canada
In 1939, the UK, Canada, Australia and New Zealand signed The British Commonwealth Air Training Plan to train pilots and crew for service overseas. About half the air crew used in British and Allied operations, including many Canadians, were trained by the BCATP.
Far from the theatre of war, Canadians began work at once, establishing 107 pilot training schools and related facilities. As well as pilots, the schools trained wireless operators, navigators, bomb aimers, and flight engineers. The scheme eventually graduated 131,000 trained personnel, earning for Canada the epithet "aerodrome of democracy" from US President Franklin D. Roosevelt.
Long before the US entered the war, WWI veteran pilot Billy Bishop set up a recruiting centre for Americans at the Waldorf-Astoria Hotel in New York. Parliament passed an Order in Council to ensure that American pilot trainees would not be required to swear allegiance to the King. By the time Pearl Harbour was bombed by Japan in 1941, about 6000 Americans were serving in the RCAF. A couple of thousand of these returned home to join the US Air Force, but many more (about 5200 in all) stayed on in the RCAF through the war.
Early on, US planes had to be purchased for training. Since American neutrality meant they could not be flown to Canada, they were flown by US pilots to Canadian border, then pulled across by horses and ferried by local pilots to their final destinations.