It seems silly: Doesn't a jumbo jet have safeguards to protect the airplane from being knocked off course by your little Nokia phone?
Really, there are two reasons you're required to turn off your phone on an airplane. The Federal Communication Commission bans the use of cell phones on airplanes because they could wreak havoc with cell phone systems on the ground.
Signals from your cell phone, when you use it on or near the ground, reach just a few cell phone nodes near you and the node that's getting the strongest signal picks up your call. If you move, while driving your car or walking, the next node picks up the call.
From the air, however, your phone's signal could reach miles, hitting many nodes at once, all with equal strength. Plus, you're moving at several hundred miles an hour. Cell phone systems weren't designed to handle that.
The Federal Aviation Administration, for its part, supports the FCC ban for its own reasons. They fear cell phones may interfere with navigation and other aircraft systems.
Incident reports submitted by airline crews also demonstrate the potential for trouble. NASA's Aviation Safety Reporting System's "Passenger Electronic Devises Database Report Set" -- which could be subtitled "passengers behaving badly" -- contains several reports of incidents involving passengers whose "personal electronic devices" seemed to create disturbances in aircrafts' electronic systems.
In some cases, whether or not a device caused a problem depended on specific location within the airplane. In one report, moving a passenger with a wireless hearing aid to a different seat solved the problem.
In controlled tests done in February 2000, Britain's Civil Aviation Authority showed cell phones can, indeed, interfere with avionics equipment on airliners and that the exact position on the aircraft makes a big difference. Interefence levels varied signicantly as cell phones were moved throughout the fuselages of test aircraft.
