Matt Unsworth offers a set of free wargames rules called The Few that he uses with his students to simulate the Battle of Britain.
Matt Fritz offers a set of fast play miniatures rules for World War II Aerial Combat.
Nigel Lancaster has written a set of abstract modern air war rules called Instant Thunder, and has graciously permitted MiniatureWargaming to host them. This is a major work, with 28 pages of rules, aircraft and missle lists, and designers notes.
Wargamer and Teacher Matt Fritz has written MiG Madness, a set of free wargames rules for playing air combat in the Korean War.
Canvas Eagles is a set of free wargames rules for WWI Dogfights