Rise of Flight (PC)
Over Flanders Fields (PC mod for Combat Flight Sim 3)
Canvas Knights (formerly Over Oleg's Fields) (PC mod for IL2)
Red Baron 3d (PC)
FS-WWI Open Plane (PC addon)
Down in Flames (PC)
Mission: WWI Combat (PC addon)
Red Baron Arcade (PC, PS3)
First Eagles: The Great War 1918 (PC)
Flyboys Squadron (PC)
Storm of Aces (PC)
Wings of War (PC, Xbox)
Richthofen's Skies (PC)
See a complete list here.