Google’s not so secret flight simulator hidden in Google Earth is fun! Whilst the controls and features are not in the same league as Microsoft’s flight simulator it is free.
To enter the flight simulator mode, press Ctrl + Alt + A ( + Option + A on the Mac)
It took me a few attempts to get it to work. I finally managed to activate it by zooming in on San Francisco!? and then Ctrl + Alt + A
Flight Simulator Keyboard Controls can be found here >>