The real reason you’re told to put your cell phone in Flight Mode

Two people using a phone on an airplane - Getty

Two people using a phone on an airplane – Getty

It is a plea heard by passengers at the start of thousands of flights around the world each day: “Please switch your portable electronic devices, including cell phones, to Flight Mode.”

Most people adhere to it, even if they’re not 100 percent sure why.

But not all of us. In a Twitter poll this week, three-quarters of Telegraph Travel followers said they turned on Flight Mode when asked, and one in four claimed it didn’t. This caused some outrage, and one user asked: “Do those who voted no really realize that it’s for their own safety? Amazing.”

But such discussions may soon be a thing of the past, as the EU recently announced that airlines can be expected to provide 5G to passengers.

The decision threatens to put an end to the relatively pleasant, phone-free aesthetic of the airplane cabin; Access to 5G will enable in-flight phone calls, messaging and video streaming.

It also raised questions about why we were prevented from using our mobile phones for so long, if they were now considered safe. Can a cell phone really crash a jet?

The Flight Mode rule seems, in part, to be an overly cautious exercise. Patrick Smith, US pilot and author of Cockpit Confidential, said: “Can cellular communications really mess up cockpit equipment? The answer is potentially yes, but most likely no, and airlines and the Federal Aviation Administration (FAA) are wrong on the safe side rather than just being sorry.

“Aircraft electronics are designed and protected with interference in mind. This should mitigate any ill effects, and to date there has been no proven phone case that adversely affected the outcome of a flight. But you never know.”

He added that devices that pose a greater risk, such as laptops, become “high-velocity projectiles during a sudden deceleration or impact.”

A person switching to Airplane Mode - Getty

A person switching to Airplane Mode – Getty

The potential for a mobile phone to interfere is not only in use but also in sleep mode, so cabin crew ask passengers to use Flight Mode.

Smith estimates that “at least half of all phones are left on during the flight, either accidentally or out of laziness,” despite clear demand at the start of each flight. However, he added that if mobile devices were such a big concern, the policy would be more actively enforced.

Cell phone use was only brought up as a possible factor after a major air crash: a Crossair crash in Switzerland in 2000. electromagnetic interference (EMI) from mobile phones”.

However, even if mobile usage isn’t safety critical, it can annoy your pilot. This is not ideal when the cockpit should ideally be a quiet and serene place. The Points Guy website quotes Nikita Schmidt, a private pilot, when discussing the issue:

“Your phone will probably annoy a few pilots and air traffic controllers. But it’s probably not bad enough for them to take action against you, if that’s what you want to know.

“You may have heard that annoying noise from an audio system that happens occasionally when there is a cell phone nearby. A phone’s radio emissions can be very strong, up to 8 W; they cause this noise due to parasitic demodulation. I actually heard this noise on the radio while flying. It’s not security-critical, but it’s definitely annoying.

“Of course there’s a lot of attenuation between the cabin phones and the pilots’ radio. However, let’s say if 50 people on board are thoughtless enough and can’t take the trouble to turn off their pocket radios, there will be 50 phones constantly searching for base stations at maximum power. That means a lot of radio pollution.

“When in-flight cellular service is available, there is a cell phone station right next to those phones. They communicate at very low power without causing any disturbance. The Wi-Fi signal is much weaker (100mW) than GSM at its peak and I’ve never heard of it causing any problems.”

So in the current system, phones have the potential to interfere with the flight crew, but only to a minor degree, though annoying. And when airlines offer in-flight 5G, that shouldn’t be a problem.

However, as Smith points out, there will be social implications.

“The moment the phones can be proven safe beyond reasonable doubt, a percentage of passengers will claim the right to use them, and carriers will pit one group of angry passengers stuck in the middle against another,” he said.

“The airplane cabin is the last refuge of relative silence. Let’s keep it that way.” We tend to accept it.

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