Yeah. I don't believe the excuse about how it could affect the navigation systems. You'd go off course everytime you flew over a cell antenna and really beware if you flew over a radio transmitter If the low power transmitter in a mobile phone could screw up the avionics that badly in a plane then I definitely don't want to be in it!

I vaguely remember somebody saying the EM fields generated by the phone can interfere with the compass. I don't degauss the TV everytime I walk past it with my phone in my pocket so it can't be that either...