Gears of Flight without the war.

http://www.flightgear.org/

The FlightGear flight simulator project is an open-source, multi-platform, cooperative flight simulator development project. This is too good to be true. If you are serious about your flight simulation you might want Microsoft's flight simulatorX on Vista with DirectX 10. If you just want to try a flght sim to find out its the most boring game ever you can try this program. When I say most boring I failed to mention train simulations. If you like planes and flying you don't have to play a high speed and stress battle sim to have a good time. This is a great place to start.