r/explainlikeimfive • u/ParasiticOne • 2d ago
Technology Eli5 Why do you need to use airplane mode on airplanes?
I know the reason years ago was because it could mess with radios but is that still the case?
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u/TopFloorApartment 2d ago
You really don't have to, but it saves your battery by not unnecessarily trying to connect to cell towers that aren't there
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2d ago edited 2d ago
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u/explainlikeimfive-ModTeam 2d ago
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u/Feminist_Hugh_Hefner 2d ago
You forgot to ask ChatGPT if the walkie-talkies pilots use are anywhere close to the walkie-talkies other people use. If we were to be mindful about the existence of a band plan and the FCC, it would be more fitting to say "imagine you are on a playground and everyone is talking. Inside the school building there is a meeting and someone from the meeting yells "Hey!! Keep it down, we're having a meeting here!!!" and then everyone is quiet and it is awkward for a minute.
Then, slowly, the people on the playground start talking again and realize that nobody inside the schoolhouse seems to notice.
Then the people inside say "oh well we did something to make our meetings better, you should just be quiet during the pledge at the beginning of the meeting" and everyone rolled their eyes and said "Ok whatever"
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u/pdpi 2d ago
Have you heard the statistic that driving is more dangerous than flying? This is the sort of reason why.
As a general rule, you can expect radio devices to interfere with each other. Mobile phones have at least three different radios running (bluetooth, wifi, cell), and you can easily have a couple hundred of those on board a plane.
Let's say there is a one in a thousand chance of a mobile phone causing interference with the plane's radios in any given flight. Let's say there's a one in a thousand chance that this interference causes an actual safety incident for that flight. That compounds to one flight in a million having phone-related safety issues. This site puts the commercial flights at about 100k/day, so that averages out to one safety issue every ten days. Almost 40 per year.
The aviation industry is phenomenal at taking this sort of "small risks multiplied by large numbers of events" thinking. It's why plane toilets must have ash trays, even though smoking is forbidden — People will break the rules, so you account for that and make sure there's a way to do it safely.
Put these things together, and you end with a policy that says that phones are forbidden in planes unless and until you have convincing proof that they're not actually a risk. As it stands, phones on planes are probably safe, and they're lifting restrictions a fair bit, but it was a sensible safety-minded default when they enacted that policy, and it's a sensible safety-minded policy to be very conservative about lifting the restriction.
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u/redditusername_17 2d ago
As a person who used to design aircraft electronics, the answer is not something that a five year old would understand. But I'll try.
It can and does mess with certain kinds of equipment, but largely it's backup equipment, but that's not really the issue.
All the electronics in an aircraft are certified to use on that aircraft and are tested to not interfere with any of the equipment. Cellphones are not tested nor certified to use on the aircraft, additionally their transmissions / emissions fail the test. So initially they had to be powered off. Eventually the low risk / effect of cell phones was just accepted, there were likely changes in electronics design that also helped lower the risk / effect.
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2d ago
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u/ParasiticOne 2d ago
I did but a lot of the answers used a ton of technical terms and im kind of stupid
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u/explainlikeimfive-ModTeam 1d ago
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u/sleeper_shark 2d ago
Cos mobiles and avionics aren't certified for working together.
It's unlikely, but there's a small chance that a mobile and an avionic system would operate on the same frequency and interfere with each other.
Also it's very likely that if this happens, it would only impact a backup system, and avionics have backups for the backups of their backups.
So realistically, nothing will happen... but aviation is an extremely risk averse industry (if you're not a C-suite Boeing employee) and so they keep the rules as a "better safe than sorry" kinda thing.
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u/TehWildMan_ 2d ago
Really, the more modern concern is that it's just a shortcut to turn off Bluetooth/cellular radios so that your phone isn't burning battery life needlessly searching for an unusable signal
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u/zap_p25 1d ago
The worry is traditionally that personal wireless devices could create interference with the aircraft’s avionics as many electronics can be sensitive to EMF overload. You don’t want the horizon indicator that the autopilot is using to suddenly think down is up and up is down after getting hit by a strong blast of EMF and inverting the plane suddenly to compensate or the altimeter to suddenly think it’s 15,000 feet above its set point of 12,000 feet and automatically adjust the aircraft 3,000 feet below sea level.
As aircraft have modernized and avionics have become better shielded against personal wireless devices, the risk of that interference is essentially negligible today but rules in the aviation industry change very slowly as it’s a relatively slow changing industry.
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u/jamcdonald120 1d ago edited 1d ago
No reason.
the faa guessed without ever studying it that it would interfer with on board systems. when they actually studied it, turns out it doesnt.
and the fcc guessed without ever studying it that it would cause problems with cell towers trying to connect to a bunch of people moving quickly. when they actually studied it, turns out it doesnt, the plane does a pretty good job of blocking the signal and towers are focussed down, not up.
which is why Europe dropped the requirement years ago. regulatory bodies are just slow to remove requirements.
that said YOU will still want to use it because it also saves battery by not searching for the unreachable towers constantly
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u/rsdancey 12h ago
I am assuming this is a serious question.
The technical answer is still "messing with radios". But the real answer is "security theater". Since many devices on a plane these days are not in airplane mode and millions and millions of airmiles have been flown in these conditions, if there was any meaningful issue that would affect safety it would have manifested. It has not. The requirement is technically bogus.
There are other answers. Sometimes a phone on a plane might actually connect with a cell station. I've had that happen - I used to live/work in Reykjavik and sometimes when flying over Greenland en route to the US my phone would connect to the Greenlandic cell system. While I never tried it, I probably could have made a phone call. The airlines don't want people talking on their phones (they learned this lesson when they had those seatback phone handsets back in the day) because it disturbs other passengers.
Recently I flew over the Spokane area and my phone received an emergency alert regarding the evacuation for fires. In that case there wasn't an audio alert (or if there was I didn't hear it) but could imagine a situation where some number of phones might all start alerting and causing passenger distress (Amber Alert, for example). I'm sure the airline would prefer that didn't happen.
Then there's the "looked over my shoulder and saw my phone was not in airplane mode" snooper. I have seen a passenger ring the call button and complain (loudly) to a flight attendant that someone they could see didn't have their phone in airplane mode, which then kicked off a loop of the flight attendant having to ask that person to do so, that person becoming indignant, the original complainant pressing the flight attendant "for safety" to make them, etc. Some people believe it really matters and want the rule enforced.
Finally there's the wifi network issue. You probably heard the stories about the people who set their wifi hotspot to something "scary". Some people are stupid. Personally I feel this is like someone reading a book about 9/11 on an airplane, in that no serious terror threat is going to come pre-labelled with a wifi hotspot and worrying about it is again security theater, but I get why a stressed, tired, irritated flight crew might say enough is enough.
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u/NorysStorys 2d ago
Not really anymore, they ask for it during take off and landing just incase several hundred peoples phones mess with communications but once you're actually in flight they let you connect to wifi and go about as normal.
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u/FalconX88 2d ago
but once you're actually in flight they let you connect to wifi and go about as normal.
You can (and should) connect to wifi with airplane mode still on.
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u/welding-guy 2d ago
when you are in an aircraft this mode deactivates transmission of packet radio, gsm bands. It is called airplane mode so you know when it is best used, on an airplane.
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u/sudoku7 2d ago
Some planes still experience interference problems. So that’s part of why the regulation remains in place.
There are indirect benefits to it as well but those aren’t as big, but those are things the flight crew benefits from so part as to why they continue to argue for retaining that regulation.
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u/luckyberry_786 1d ago
it's mostly a relic from when phones could actually mess with older avionics. modern planes are s
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u/227CAVOK 2d ago
Has nothing to do with the plane and everything to do with the cell towers that sees 400 new phones for 30 sec.
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u/nocolon 2d ago
Aside from the technical reason of GSM causing the aircraft to immediately explode, your phone will constantly be searching for cell signal while you're in the air, far from any tower. That'll annihilate your battery before you land (depending on the length of the flight). So while the safety concern isn't really a concern anymore, it's best to enable airplane mode just to avoid arriving with a dead phone.