Why do you have to put your phone on airplane mode before take off?

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Why do you have to put your phone on airplane mode before take off?

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There were concerns about the radio communications between the phones and towers possibly interfering with critical communications on the aircraft.

The claims are that it can interfere with the aircraft equipment. Even if it’s a miniscule amount. Of course there will be some people who don’t do it but it probably takes hundreds of phones to cause any significant interference.

There are essentially two reasons airlines ask you to turn on airplane mode and stop playing with your device before take-off and landing: 1/ because 20 years ago, devices such as cell phones could interfere with the aircraft’s systems and potentially wreak havoc on your flight. 2/ The crew wants your undivided attention as the two most dangerous times on a flight are take-off and landing.

Nowadays, with modern phones and airliners, the first justification no longer holds water, so they’ve switched to using the second justification.

It’s an old law from FCC when cell phone towers were first created.

A single cellphone on the ground might be able to communicate with two or three towers at the most. A cellphone 36,000 ft in the air could communicate with hundreds.

This created extreme problems with the phone network, essentially shutting them down. I forget the technical term for it but it’s like when 200 routers say, ” yeah I know that computer. let me get in for you.” and it starts an endless loop.

As an RF communications engineer/repairs for the past 20 years, I feel confident in saying it doesn’t affect the airplane. My cell phone, at max only puts out 3 watts ( usually only 0.5ish watts ). This is very little compared to the multiple of 500 watt tower that they must take off of through fly above and then land back in.

There are also federal regulations that allocate certain frequency bands to certain groups. airplanes and cell phones don’t operate on the same frequencies.

The real answer is because government is really slow to update its policies. The airplane mode policy is from an FCC regulation implemented in the 1990s (47 CFR I(b)22(h) 22.925. That regulation bans the use of cell phones on planes in order to “protect against radio interference to cell phone networks on the ground.” Meaning at 40,000 feet in the air, active cell phones would be picking up service from multiple cell towers on the ground while passengers are traveling at high speeds. This makes the cell phones work poorly and interrupts the regular use of those towers by adding random draws on the signal. This could crowd the networks on the ground and disrupt service. This justification is not warranted any more, but there are reports of some noise heard by pilots during communications with towers so the FCC has just left the policy in place.