[long answer]
...You really don't want to use a physics engine for a flight sim. I've made quite a few using GS. My first project with GS was actually recreating the Wright Flyer in Kittyhawk, NC. My most recent project was a WWII flight simulator inspired by A) Return to Castle Wolfenstein & B) my new Joystick. The flight sim turned out great, but I ran out of ideas for the game. I had even added an unlimited terrain system. If I ever decide to open it up again, I'll probably post some videos, and then release it to the community...

[short answer]
Yes, GS works just fine for flight simulators. It's about the programmer, not the language...