They have the POTENTIAL to interfere with navigation/communication systems as they operate on a close frequency/wavelength. Once, my captain could clearly hear a woman in back talking to a friend over his headset! In fact, the womans name was used in the conversation and he had to ask "Barbara" to please discontinue use of her phone for departure over the PA. Phones transmitting near the 1700 Mhz range were found to have caused these incident on aircraft: · Slaved Compass froze or overshot actual magnetic bearing · Needles on instruments (engine/aircraft & nav) appeared unstable · Digital VOR bearing display showed errors of 5 degrees · VOR to/From indicator reading was reversed . VOR & ILS course indicator errors with & without a failure flag · Sensitivity of the localizer was reduced · Background noise in the audio system · False warnings of unsafe conditions such as smoke alarms in the baggage compartments Here are some interesting links on the subject- Effects of cellular phones on aircraft avionic equipment": http://www.caa.co.uk/docs/33/capap2003_03.pdf http://www.cs.ccsu.edu/~pelletie/local/news/telecom/Cell_phones_on_planes.html

Yes they can, especially if a lot of people are using them. Radio frequency might be affected especially when transmitting data from the earliest time the plane lands or takes off. Almost all communication equipment has the capacity to interfere frequencies of other devices but not on the same level though.

There is no solid evidence that cell phones or other devices like it such as ipods or portable gaming devices will cause interference, it is more of a concern and precaution. When using mobile devices on an airplane was first band there might have been more of a chance that a phone call could have possible caused interference, but as the flight systems on aircraft became more advanced the threat of cellular interference decreased dramatically. In a few year you may start to see phones being allowed to remain on during flights, and possibly being able to connect to an in flight air-to-ground communication system allowing you to make phone calls or send a text message during the flight. This is not a new concept ether, some European and Asian countries have already introduced similar features aboard most there aircraft.