Originally Posted by Loren Pechtel
It's a matter of distance. A cell phone on an airplane puts a lot more radio energy into the plane's electronics than the big tower on the ground.
Not once you get to the "far field", which is the area beyond a sphere of about 1 meter or less from the cell phone's antenna.
The energy radiated by a cell phone in the far field is 1)very tiny and 2)in another frequency band than the frequency band of the navigation and communication systems of the aircraft. The harmonics' (multiples of the cell phone's frequency) energy in the communication and navigation frequency bands is so small that it is zero for all practical purposes.