No idea for how long this has been around, but I only today discovered the flight simulator in Google Earth. Yes, there is a (quite basic) flight simulator built right into Google Earth, starting with version 4.2. There is no sound at the moment and only a few basic moves, but you can at least use your mouse (I prefer it over the keyboard) or even a joystick. You'll want a fast internet connection, too, and probably some basic experience flying a flight sim. Well, my experience stems from F/A Hornet back in 1998, but it's enough to keep me in the air.