"First Light" by Geoffrey Wellum is a great book. Tells about his training in 1939 (RAF) and then the Battle of Britain. REalLy GOOD!
"Saggitarius Rising" by Cecil Lewis. About a pilot's experiences of the First World War. SpLEndid!
Both the above should not be too hard to find and are probably the best ever military flying books. Really well written.
Also agree about Chickenhawk