It is a fact that there is zero evidence that cell phones have any effect on flight control or navigation systems. Thats why there is no FAA regulation against the use of cell phones on airplanes.

Think about it. If cell phones could actually cause a significant problem on an airplane that might in any way affect our safety, we would not be allowed to have them on board. Every once in a while I forget to turn my phone off. It remains on during the entire flight. No one checks my phone to see that it is off. It's a voluntary process. If it could cause danger, it would be a mandatory, regulated process.

Ironically, a laptop PC that has been worked on and not reshielded, causes far, far more EMR than any phone. Yet we can use our PC's while in flight.