21st June 2004 - For mobile phone users, the anytime-anywhere freedom of being able to talk on a cell-phone has always stopped at that moment when an airplane leaves the gate and taxies out onto the runway. Citing safety reasons, aviation authorities and airlines have said that mobile phones risk interfering with airplane avionics*, and should not be used during flight. However, there is little evidence to prove that use of a mobile phone on a commercial flight presents a real risk, and if some have their way, in the next few years you may be able to use your own mobile while in flight.

While some in the aviation community have accused mobile phones of interfering with navigation gear and radios on flights, to date there have been no definitive instances in which use of a modern digital mobile phone by a passenger outside of the pilot compartment has been linked to a problem with an airplane's avionics. Nevertheless, aviation authorities have adopted a "better safe than sorry" attitude toward mobile phones and have banned their use outright during flight.

The fears related to mobile phone use during flight can be traced to the fact that Radio Frequency (RF) transmissions from some devices can interfere with the operation of other devices that also rely on over-the-air transmissions. This is the basis of government regulation of the airwaves, which is designed to ensure that various users of the airwaves (TV, radio, mobile phones, for instance) operate on different frequencies so that they won't interfere with each other.

In some instances, some mobile phones have been shown to interfere with avionics when used next to (within 12 inches of) the radios and navigation gear. Interference typically includes "noise" such as popping or hissing that a pilot may hear over the radio. Certainly no pilot would want to hear distracting noise, particularly while engaged in communicating with the ground or while taking off or landing. Another fear is that RF from a mobile phone might drown out the low power signals that navigation gear receives from satellites, such as GPS signals. The obvious remedy, based on available evidence, to ensure this doesn't happen, would be for all the personnel in the pilot's cabin to turn off their mobile phones while in flight. Since passengers on commercial flights are typically not able to get within a dozen feet of the avionics, their use of mobile phones would present no risk to the flight from that standpoint.

Mandates against using mobile phones rely on tests conducted in the early to mid-1990s, when nearly all mobile phones were analog-based, and transmitted at higher power levels. Tests to determine whether modern digital mobile phones, which transmit at fractions of the power levels of older analog-based handsets, have not been conducted. Never has an instance where an interfering event in the passenger cabin related to a mobile phone have been able to be repeated - repeatability being one of the key tenants of the scientific process. There has never been an instance of mobile phone-induced interference in the passenger cabin being repeated - and repetition is one of the key tenants of the scientific process.

Use of mobile phones on airplanes does present substantial risks though - not to the airplanes, but to mobile phone networks on the ground. While a mobile phone won't crash a plane, if everyone on a plane is using a mobile, they will crash the cell networks as they fly over them. The problem is that cellular phone networks were never created to perform hand-offs on 500 MPH phones. Even worse, the capacity that each mobile phone uses in a plane is gigantic - potentially a mobile at 30,000 feet could be trying to contact not one or two or three cell towers at a time, but hundreds, or even thousands. Multiply the number of passengers in a 767 or 777 by the hundreds of airplanes in the air at any one time and the potential for catastrophic interruptions of the cell networks is huge.

As former FCC Chief of Engineering and Technology Dale Hatfield said when informed that people using mobile phones in private planes had experienced no problems: "How do they know? They could affect people on the ground and not know it."

A solution to the problem of airborne mobile phones interfering with terrestrial mobile networks is the use of an airplane-based base-station that would receive and re-transmit mobile phone calls from the airplane to the terrestrial networks. Companies such as AirCell have developed technology that allows passengers to use their mobile phones to make calls while flying. AirCell plans to put small base stations on board commercial aircraft. The base stations capture the signals from passengers' own mobiles and retransmit them to specific base stations on the ground. The beauty of the system is that it prevents mobiles on board the plane from swamping the cell systems on the ground, and also causes the mobiles to transmit at their lowest power settings, thus reducing the risk of interference with avionics.

The outlook for using mobiles on airplanes is not great at the moment though. Aviation rules governing how commercial aircraft operate allow airlines to ban the use of mobiles at any time on an airplane, at their own discretion. Airlines are unlikely to change their minds about use of mobiles on an airplane when there is no evidence that mobile phones do not have a detrimental effect on avionics. Even if an airline were to change its mind on the issue, insurers would prevent airlines from changing policies governing the non-use of mobiles on flights. The end result of this is that currently, the only place that you will be able to use your mobile or see an airborne base station technology such as AirCell's deployed is on private and charter planes. So next time you jump a Gulfstream or a Lear jet, be sure to leave your mobile on.

Back to News Reports