Knights of the Sky is a Microprose game from 1990 – somewhat inferior to Red Baron, but a bit simpler and easier to play.
Fly as a Allied WWI fighter ace, over the western front, randomly encounter enemy planes and balloons, and as you can kills and notoriety, enemy aces will try to hunt you down (and you can hunt them down!) Also features head-to-head dogfighting via modem (1990!)
Although, there are probably like 15 flying games to choose from, including Red Baron, Flying Corps, to WWII ones like Secret Weapons of the Luftwaffe, 1942 pacific air war, Their Finest Hour: The Battle of Britain (which leads directly into some unknown games called X-Wing and TIE Fighter)
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