They are now prohibited on alot of US carriers. There have been instances of passengers causing a commotion of airplanes being off course when in reality, the aircraft made a turn to a specific heading and the passenger didn't understand quite how to use the GPS properly.
OK I saw the following post in a Yahoo Group Deal and I was just curious can this really happen? Or can it effect the Aircrafts GPS Computer at all? Also what are some Good GPS Devices besides your cell phone.