This argument I believe is ill-founded! Of course you can use a GPS on an aeroplane of any kind. Yes the GPS unit does emit EM radiation as any electric device does. However, as for the argument that this radiation knocks out certain systems in the aircraft is ill-founded. Lets face it, EM radiation including radiowaves are present everywhere in the environment. Pilots should be more worried about high energy cosmic rays that can change logic sequences and corrupt data than someone with a GPS unit or even a mobile phone on board.