Both Britain and France were class based societies at the start of the war and it was presumed that only gentlemen possessed the intelligence and independence of thought needed to learn to fly. Future pilots were therefore predominantly recruited from the more privileged classes. In Britain public schools were recruiting grounds for future pilots. Among those already serving, probably only a junior officer would be considered. He would face the suspicion that he was volunteering primarily for the opportunity to return to a safe area for training. This was a odd perception since flight training at the time produced proportionally more fatalities that the front lines. At the start of the war, training was truly minimal. To reassure the fledgling pilot, the first lecture was often a description of how flying was very like riding a horse. The primary trainer was the "longhorn" "https://en.wikipedia.org/wiki/Farman_MF.7" and a new pilot might expect to have 25 solo hours before reaching a front line squadron, none of it on first-line fighter aircraft. Later in the war, this would rise to 50 hours with perhaps 5 in a fighter. It was presumed that final training would occur in the operational squadron. The Royal Air Force Museum website has some information on the early training regimen. "http://www.rafmuseum.org.uk/research/online-exhibitions/taking-flight/pathway-to-pilot/pioneering-years.aspx". An excellent and largely accurate historical fiction novel that includes British early pilot training is "The Larks" by Jem Shaw and Martin Shaw.