Cheapest and easiest to get into is probably the aforementioned
Wings of War. The movement system using cards is interesting and innovative (keeping in mind that I haven't played a lot of aerial combat games

).
Basically you have different maneuvers your plane can do, and each plane is different (for example some do long left turns, others can go faster straight ahead, etc. - all fairly historical accurate from what I've heard). You queue up 3 maneuver cards, and then play them right on the card representing your plane. Eh, a picture is worth a thousand words, so basically:
Thinking of your orders ahead of time adds a fun "outguessing" aspect as you try to think of where your opponent will go. It also means you can awkwardly circle without firing sometimes.
Anyways, a fun quick game, but it might not have the depth you want for super long play (although more planes, more expansions, and more objectives can help that). The
rules are free on the official site (obviously not much use without the cards), so you can get a better idea from those.
Now I'm going to go check out Canvas Eagles, because it seems neato.