In the early years of the war it was realized that it was too dangerous to train pilots and air crews in Britain so the BCATP was created and Canada became the primary place to train almost all British commonwealth pilots and crews throughout the war. Some 132,000 personnel were trained to fly and crew fighters, bombers and ground crews.
It proved to be very successful and even many thousands of Americans were trained as well under incentives provided by both the American and Canadian governments. In addition other countries sent aircrew here to Canada to train. The program was so successful that it even continues to this day almost all NATO countries and most former commonwealth countries still send pilots here every year to train.
Missed opportunity for a British Tea joke (such as the British were extremely delighted to see that the Germans wanted nothing to do with the disgusting liquid called Tea and left it all to the British as a punishment after their capitulation) and a French baguette joke.
Also in Canada and Rhodesia it also was perfectly safe to train in bright yellow Harvards/T-6s. This is a massive advantage as these are easy to spot and in case of an emergency landing easy to find back. We cannot underestimate the advantages of a safe training environments