Just to throw something else into the conversation, although GPS is still being trialled as a "primary" navigation means, using satellite's to navigate is not new.
Commercially on pacific routes from west coast of USA out to NZ and Aus, FANS (Future Air Navigation System)is being used. Basically a little black box on the aircraft recieves and transmit data via satellite. The data that is transfered, such as position of aircraft, height speed is combined with weather data and sent back to the aircraft to give the best route accross the pacific and maintain aircraft separation.