Dawning of the Jet Age is a set of free wargames rules in an alternate World War II that continues on until at least 1946. In this world, German and Allied jets fight it out for air superiority over Europe.
jets
Instant Thunder Air War Rules
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.