Really good looking game and specially Hard difficulty is very thrilling when you play in cockpit view :)
only 2-4 suggestions from my side:
try to put clear reflection on those cockpit mirrors, so you can see who is on your tail and include a pilot inside for cockpit view and animation pilot's hands using throttle and flight stick. Finally last and a big one : an airfield, you taxi out of hanger to runway, and take off, and after mission is completed you land your jet :)
Overall very good looking game and i'm hoping you will become one of the best developers of air combat genre games, well you are half way there! :)