Aces High
I've watched this one many times. Some wonderful flying sequences set to stirring music, and very, very sad.
It's Journey's End rewritten to be about the RFC rather than set in the trenches.
But my favourite would have to be The Dambusters. When I was about 10 I saw the film, then got a copy of the book which I learnt almost by heart and used to annoy my family by reciting chunks of it. I can still remember most of it now.