I'm going to get way over my head very quickly, because while I spend some of my days playing with fancy toys to produce radio news, I leave most heavy lifting beyond the "ON/OFF" and "RECORD" switches to the engineers who know what all those little electronic doodads behind the face of the control panel are.

Essentially, however, every radio receiver beyond the crystal sets of the early 20th century is also a radio transmitter. That is caused by the physics of the circuitry that is used to amplify, discriminate, and make useful the signal coming in from the antenna and it is an unavoidable side effect.

There is a small possibility that these low-power transmissions, even though they are tiny fractions of a watt, can affect some of the navigational instruments of an aircraft, so to be "better safe than sorry" many airlines insist that all radio receivers are supposed to be turned off when an aircraft is in flight. This applies to AM, FM, TV, -- and GPS.

Cell phones, of course have both a receiver and a transmitter hundreds of times more powerful than these side-effect transmissions, so they're prohibited also. They don't work well in the air anyway, because the terrestrial infrastructure of the cell phone system wasn't designed to handle a caller moving from cell to cell at 500mph or calling from an altitude that causes the signal to reach many more cells than a ground-based signal.