Portable Electronic Devices on Aircraft

A Safety Concern
The ever-increasing popularity of portable electronic devices (cellular phones, laptop computers, video games, DVD players, etc.) and the frequent introduction of new devices cause concern among aviation professionals when those devices are brought aboard aircraft.   Certain “PEDs” have the potential to cause electro-magnetic interference (EMI) with aircraft electronic systems.  If strong enough, EMI can cause cockpit instruments to display incorrect readings and other anomalies.  Although PEDs are known to be capable of causing EMI, the effects depend on a number of variables and often cannot be duplicated.  Pilots have reported numerous events in which a PED was suspected as the source of interference, and some have claimed that problems stopped when a crew member asked passengers to turn off their PEDs.  However, efforts to prove that a PED caused  interference often are inconclusive.   Due to the mercurial nature of EMI and its potential to affect flight safety, measures to control it necessarily are conservative.
History
The Radio Technical Commission for Aeronautics (now RTCA, Inc.) began an investigation of PEDs in 1983 that culminated in publication of a report in 1988.  It concluded that signal emitters such as cellular phones, remote control toys, and citizen band radios could cause interference and should be banned from aircraft.  The RTCA found no compelling evidence of interference from PEDs that do not emit a signal, but nonetheless recommended they be banned from use during takeoffs and landings to assure an added margin of safety during those critical phases of flight.
In January of 1992, the Air Transport Association (ATA) petitioned the FAA to adopt the RTCA recommendations as a federal regulation.  However, FAA opted for further study and commissioned RTCA to resume its efforts.  In 1996, the RTCA published the second study on the use of PEDs and made the following recommendations:

1. The FAA should prohibit the use of any PED during any critical phase of flight. Additionally, any PED which has the capability to intentionally transmit electromagnetic energy should be prohibited in aircraft at all times, unless testing has been conducted to ascertain its safe use.
2. PED testing efforts of existing and new devices (such as satellite communications and two-way pagers) should be continued by the FAA, the airline industry and related manufacturers to further understand their potential to interfere with aircraft systems.  
3. A public awareness campaign should be initiated by the FAA, the airline industry and related manufacturers to educate the public about PEDs and their potential interference hazards, especially those designed as intentional radiators or transmitters.
4. Government and industry should pursue research into the design and feasibility of detection devices to locate emissions that produce interference within the aircraft cabin. 

The Current Environment

Today, it is common for the majority of passengers on an airplane to carry one or more PED, such as iPads, Blackberries, laptops, Kindels, etc..  Simply by being “on”, these PEDs emit electro-magnetic energy, but usually at power levels too weak to cause EMI.  They become an EMI concern and require control if they merely have the capability to actively transmit signals, even low power signals (eg, laptop wireless connection modes).  Adding to the need for controls, passengers may not know if their device is in a mode that transmits, nor can we expect flight attendants determine if a particular device is transmitting.  Concerns over EMI remain greatest for PEDs that can transmit high-power signals, such as cellphones.  In addition, FCC regulations prohibit the use of cellphones during flight due to problems that their use causes with the cellular network on the ground. 

Airline Policies

Federal aviation regulations (eg, 14 CFR 91.21) require airlines to determine whether or not PEDs brought aboard their airplanes could cause interference problems, and control PED use accordingly.   Each has adopted its own policy, but in meeting this responsibility airlines typically follow the RTCA recommendations.  In general, devices having little potential to cause EMI and those having  a capability to transmit at low power (eg, laptops) must be turned completely off during flight below 10,000 feet as that regime includes takeoff, approach and landing where EMI could cause the most significant problems.  Policies and FCC regulation require that high-power transmitters (eg, cell phones) be turned completely off during flight. 

Source: Air Transport Association