Not sure which war you're focused on here. If its 2, my father enlisted direct with the RAF ( not RCAF) in Spokane, Washington. He trained in southern California, then took a train to Nova Scotia and shipped over to England. He was serving as a Flying Sgt with the RAF in 59 OTU when the Army Air Corps finally got organized in England in Sept '42 and took most of the Americans from the RAF. He was one of many and there are many books about them.