I must be sadder than I realised - I've read most of the books this list has thrown up so far...
One more deserves a mention. For those who enjoy the WW1 period - Insall (Observer) or Lewis (Saggitarius Rising) for example.
Winged Victory by V. M. Yeates
I'll guess it will be very hard to get hold of a copy now but it would be well worth searching out.
Yeates died of TB shortly after finishing the book (early 1930's). During the early days of WW2 fighter pilots were reputedly forking out a fiver for a copy - it's descriptions of flying combat being especially well written.
JB