Why Do Phones Have To Be on Airplane Mode During Flights?

Millions of people are mentally preparing themselves for holiday air travel, an already-bewildering experience made even more stressful by flight crews demanding that you set your phone to airplane mode. Most of us accept that doing so has something to do with preventing a plane crash, and so we comply, albeit begrudgingly.

In a way, that grumbling is totally justified. The reality is that leaving your phone’s communication systems on will probably not cause your plane’s systems to fail or the aircraft to crash. What it will do is really, really piss off your pilot, who may not see you trying to receive messages on your phone but can almost certainly hear it.

The reason flight crews are so adamant that passengers set their phones on airplane mode is that the radio signals received by phones using what’s known as GSM, the wireless tech found in more than 80 percent of phones worldwide, will audibly interfere with the plane’s own radio communications systems. When that happens, the sound that floods a pilot’s ears is very much like the sound you hear right before a cell phone next to a hi-fi speaker or car radio starts to ring: that annoying, telltale blip-blip-blip, followed by a screechy buzz.

That annoying buzz is the sound of a cell tower signal and your phone trying to communicate with each other in the air. The signals traveling between them travel in pulses, and when those pulses are strong enough and pass very near a piece of radio equipment — say, the radio your pilot uses to communicate with ground control — they can be accidentally detected by the amplifier inside it.

The amplifiers inside radio equipment are designed to pick up only radio frequencies, but if a cell phone signal is strong enough and in very close proximity, the amplifier will pick it up anyway and and convert it into an audio frequency, which is ultimately what your pilot hears.

Signals flitting back and forth between a cell tower and a single phone may not pose much more than a minor annoyance to the flight crew, but the audible effect of hundreds of signals traveling through the equipment could seriously hamper the plane’s ability to communicate with ground control — as well as test your pilot’s patience.

There is a certain point — one that’s largely dependent on altitude and your distance from land — where the benefits of putting a phone on airplane mode are greater for the passenger than they are for the pilot. Cell phone signals are only strong enough to travel 5,000 to 10,000 feet into the air; past that point, your phone can’t interfere with plane radio if it tries. Nevertheless, it will frantically continue to try finding a signal, and the futile search will rapidly drain your battery.

The benefits to defying your pilot’s request for airplane mode are extremely limited. If you’re that desperate to receive messages during flight, it’s probably worth it to shell out the extra bucks to get on the plane’s Wi-Fi, which communicates with your phone using signals that are far weaker than those sent out by a GSM phone, so they don’t bother the pilot. On the rare flights where phones are not required to be set to airplane mode, airplanes are equipped with miniature cell phone towers called “picocells,” that channel signals from the ground to improve reception on the plane.

While it may be difficult to be separated from the internet for a few hours, it’ll probably be much less of an ordeal than the existential stress that accompanies the holidays. As the number of psychological problems related to incessant cell phone use continues to mount, the chance to go on airplane mode could be the season’s greatest gift of all.