Devices May Interfere With Planes in Flight

Electronic devices like cell phones and music players could interfere dangerously with airplane avionics, according to a recent investigation, despite increasingly blase passenger attitudes about switching them off.

Although no air crash has been definitively linked to such interference, safety experts cited it as a possible cause in a 2003 crash in New Zealand. The pilot was making a cell phone call during landing when the plane crashed short of the runway.

Since 2000, at least ten voluntary reports filed by pilots in the U.S. have linked interference with instrument problems, but such evidence tends to be circumstantial. Engineers have expressed concerns that older aircraft -- a plane's service life can extend for decades -- may not be adequately shielded against modern mobile electronics.

The Federal Aviation Administration acknowledges the potential for harmful interference from electronic devices, and requires them to be switched off when flying below 10,000 feet, when pilots would have less time to correct for problems. At higher altitudes, airlines can dictate their own policies.

"There's not enough evidence to warrant a change," said Les Dorr, an FAA spokesman.

All electronic devices emit signals with the potential to cause interference when powered on, though phones and Wi-Fi-enabled products which transmit radio signals by design generally radiate the most power.

As mobile devices become more deeply integrated into everyday life, the idea that they could crash a plane becomes harder to imagine. There's no recent data on how many passengers may ignore warnings to turn off electronics during takeoff and landing, but a study seven years ago found that cell phones were often left on for the duration of flights.

Although all airlines must require passengers to shut down electronics at lower altitudes, a growing number offer Wi-Fi Internet connectivity in flight, including American, AirTran, Delta, JetBlue, and Virgin America.

Common sense suggests that, given the sheer volume of air traffic, there must be thousands of devices left on during flights every day. This is particularly true now that many modern products actually enter a lower-power sleep state when turned "off." The airline industry's excellent safety record indicates that serious cases of interference, though impossible to rule out, must be rare.

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