Personal electronic devices or PEDs, give off electromagnetic signals when operating. These signals might interfere with various in-flight aircraft systems, including communication, navigation, and on-board radar. During takeoff and landing, it is crucial that these systems operate properly, as pilots have little time to react to malfunctions if they occur.
Although iPods and e-readers may not have a communication function, the crew will still alert you to not use them. Cell phones will operate from an aircraft cabin while you are on the ground and within the range of a cell tower. However, your conversation is just one more electronic signal among many others, and might be picked up by the aircraft communication system. Pilots need a clear and uninterrupted dialogue with air-traffic controllers in order to execute safe takeoffs and landings; they must also keep up communication with control towers along the route.
By regulations passed by the Federal Aviation Administration (FAA), you are allowed to use electronic devices once the aircraft has reached an altitude of 10,000 feet. At this stage of your flight, the flight route has been established and the pilots have more time to deal with any electronic interference that might arise, and can react by requesting that passengers turn off their devices. The use of cell phones, which can more directly interfere with communication systems, is banned throughout the flight.
Jet aircraft depend on dozens of on-board control systems, including a GPS positioning system, an autopilot computer, rudder controls, and cabin readouts of fuel supply, altitude, and other essential information. Although passenger devices have not been implicated in any incidents or crashes, consumer electronics is a constantly evolving field, and the possible interplay of newer devices and existing onboard systems is not fully understood.
The FAA does not restrict the use of certain devices that have been found to not interfere with aircraft systems. These include portable recording devices, heart pacemakers, hearing aids and electric shavers. Also, newer cell phones have an "airplane" setting in which the user can operate certain functions of the phone but not use it for voice transmissions. This is the one exception to the rule banning cell-phone use throughout your flight.
