Wings of war. Of all the 'casual' wargame like games ive played this one is superb. Simple to play (pick a plane from WW1 era) lay maneuver cards, if your in range take a damage card, apply special damage (if any) bang done.
Fantasy flight games produces. There are two version - WW1 (Famous aces, Watch your back and burning Drachens) with a number of supporting pewter aircraft (3 series approx 18 planes per series split between allies and the hun. Then the WW2 version = Dawn of war with spitfires and other craft of the era. Not as well supported in terms of actual pewter aircraft so you'd be more likely to use the plane cards rather than models.
We run it along side our usual 40K games and it goes down really well. You can have 2, 4, 6 , 10 a side and not loose much