Flightgear - free open-source multi-platform flight simulator

Gacked from the Oolite forums.

I don't have the patience for flight simulators, but for those who do there's just been a new release of Flightgear, which looks pretty good. Runs under Windows, Mac and Linux and other platforms, and it's free unless you want to buy it on disk. People who know these programs say that it's pretty good, and there are tons of aircraft available including the Space Shuttle, SR-71, fighters, helicopters, etc.

http://www.flightgear.org/

Some videos here that are a bit more recent than the ones linked from the Flightgear site:

https://www.youtube.com/watch?v=KwFSm3zYfCs

https://www.youtube.com/watch?v=nSYOdx4s0xo

https://www.youtube.com/watch?v=oHlbUS8ovpk