Since it's a receiving device only (unlike mobiles etc.) there should be no problem using a GPS on an airplane, as long as you stick to the usual rules (not during takeoff/landing).. .Be prepared, however, to quickly turn it off when told so by the cabin staff! We've had some funny things happening during a flight and found out after asking everybody that 3 (!) people had been using GPS-receivers in the cabin at the same time.. .A good thing would be to ask in advance just to let everybody know you're using it...