Owners of iOS devices might be interested in Sid Meier's Ace Patrol, a First World War combat game for iPad and iPhone. It's turn-based rather than a flying sim, along the lines of the tabletop game Wings of War (which I own but haven't actually played): you make your move (fly, bank or shoot), then the computer-controlled enemy gets a go.
I've only had a brief play so far but it's rather cute, with nice graphics. You can choose a female squadron leader, which is the kind of historical inaccuracy I can get behind.
The game is free but you have to pay for upgrades, special paint jobs, and the ability to play right through the war.