9 ms·

Note that the reason for airport mode is a courtesy to cell-phone carriers. It's not any air safety issue. Rather, 300-500 cell phones all trying to contact t

Note that the reason for airport mode is a courtesy to cell-phone carriers. It's not any air safety issue. Rather, 300-500 cell phones all trying to contact the next cell tower, multiple times per minute, would wreak havoc on cell service. https://www.inverse.com/article/51015-cell-phone-use-on-airplanes-airplane-mode-thanksgiving-travel https://www.inverse.com/article/51015-cell-phone-use-on-airp... At one point, when both cell phones and laptops were new, there was perhaps a risk to the airplane's electronics. Modern cell phones have been steadily tuned to reduce interference with other electronics though - good thing, otherwise you couldn't use them in a modern home with its dozens of connected devices. And modern avionics have been shielded to protect them from outside electronic interference - also a good thing, otherwise the next terrorist could simply turn their laptop on. The ban on electronic transmission is one of those regulations that was a response to technology at a particular point in time but now is largely vestigial. You can tell because it's rarely enforced, and yet bad things do not occur just because you forgot to turn your phone to airplane mode.

alexnewman 4y ago
luckily this happens all the time since people often forget. i know i do.
sigwinch28 4y ago
> Note that the reason for airport mode is a courtesy to cell-phone carriers. This doesn’t track. What about trains?
- joecot 4y ago
  Trains move significantly slower than planes. They're also on the ground, mostly below the towers, while planes are in the air, moving very fast, with multiple towers in line of sight.
- scandinavian 4y ago
  It doesn't track in any way. In the airport there's small cells or femtocells by the operators. In the air, the only cells you can reach are the one pointing upwards. Also, they don't really ask for airplane mode anymore, at least not when I'm flying.
- gnfargbl 4y ago
  The cell tower network is designed to cope with devices located on the surface of the planet, i.e. where the geometry between the handsets and the tower is roughly two-dimensional. I am also unconvinced that handsets on aeroplanes are really a problem for the network, but trains aren't the counterexample you're making them out to be.
  - Kye 4y ago
    Flight patterns are also pretty consistent. Tower planners have probably given some thought to it.
    - afavour 4y ago
      That doesn't address the 2 vs 3D problem the person you’re replying to outlined.
    - samdcbu 4y ago
      Cell towers are designed for terrestrial users because their radios aren’t pointed at the sky. Gogo provides inflight Wi-Fi in the US through its ground based towers and all the antennas are pointed at the sky :) Flights (at least in the US) fly roughly a direct route, but ATC spaces out planes and small weather diversions are common. So it’s more like a band of coverage needed between cities. Also, the combinatorics of considering every US city pair that currently or has previously had commercial service between gets long. Then you would have to consider every route that an airline in the future may offer, even just seasonally. Then if you calculated the optimal route between each pair and figured out the width of the cellular coverage at 30,000 ft from a single cell tower below, I don’t think it would be possible to offer service to every domestic flight in the US without achieving complete coverage of the US. China on the other hand has a limited number of very narrow flight corridors that all commercial aviation is restricted to because the majority of the airspace is government controlled. That’s the only nation I can think of that would have enough air traffic to justify terrestrial tower installation but whose domestic flights are confined to a such a small part of the airspace that it would be possible to provide service to all domestic flights without achieving coverage of all Chinese airspace.
- nostrademons 4y ago
  You're supposed to put your phone on airplane mode in a train or subway too, but most people don't: https://pocketnow.com/airplane-mode/ https://pocketnow.com/airplane-mode/ The problem is significantly lessened for trains vs. planes though because you're traveling an order of magnitude slower and hence you switch cells an order of magnitude less frequently. Also many commuter rails run alongside major highways or boulevards, where the cell systems are built assuming lots of cell handoffs at roughly highway speeds. If enough people used high-speed rail to overwhelm the cell system we'd probably see announcements to put phones in airplane mode there too, but very few folks will travel long distances at high speeds on a train.
  - Bluecobra 4y ago
    That article sounds like a bunch of hogwash to me. The CTA in Chicago specifically has cell phone infrastructure in the subway lines, and that predates that article. https://www.transitchicago.com/cta-to-bring-4g-wireless-service-to-subways/ https://www.transitchicago.com/cta-to-bring-4g-wireless-serv...
  - hocuspocus 4y ago
    > You're supposed to put your phone on airplane mode in a train or subway too, That's a pretty insane claim in most of the world. Lots of people expect and enjoy full coverage on train or subway rides. I work at a carrier and the signal strength and cell capacity on trains are part of the top metrics we use to benchmark the quality of our network and the customer experience.
    - brewdad 4y ago
      > You're supposed to put your phone on airplane mode in a train or subway too, Why would you be expected to do this when we don't require drivers to put their phones in airplane mode? I get that US trains are slow compared to other parts of the world, but does the Autobahn require airplane mode? Doubtful since my German car happily connects to my phone in multiple ways.
    - danw1979 4y ago
      >> You're supposed to put your phone on airplane mode in a train or subway too, > That's a pretty insane claim in most of the world. So is this: > but very few folks will travel long distances at high speeds on a train.
- henrikeh 4y ago
  Cell phone cells are (ideally) shaped to account for the expected pattern of how handover will occur. Along roads and train lines, the cells are (at least in GSM) supposed to be tailored to allow for easy routing and handover as the devices travels in the direction of the way. While I have never read anything concretely analyzing the handover pattern of devices on airplanes, I would expect that since a very large number of cells are almost equally visible/equal signal strength, the network would have to frequently handover the device from one cell to another. The handover process is, for voice traffic, very resource intense. (in GSM) it involves duplication of traffic to the neighboring cell and a lot of coordination. I think that could be the reason for why mobile operators find airplane-borne devices annoying.
- dsr_ 4y ago
  Line-of-sight. If you're 4-5 miles up with no blockers except the aircraft skin, you get to confuse a lot of towers at once.
  - hombre_fatal 4y ago
    Must not be very much of an issue since there’s basically zero messaging around what airplane mode is for. Not once has any of my carriers even said “please turn on airplane mode to help the network”. Instead it’s an in-passing recommendation made by air stewardesses so boilerplate it feels like superstition. I wonder what the actual impact is and how that relates to the low effort messaging around airplane mode.
- xani_ 4y ago
  Compare the speeds of both modes of transport
- enumjorge 4y ago
  And movie theaters, malls, stadiums. Maybe I’m missing something?
  - matthewmacleod 4y ago
    If you're in a stadium travelling at 600mph, you have a heck of a problem! I think the challenge isn't so much "lots of people in one place" as "lots of people travelling extremely fast with line-of-sight to hundreds of cellular towers at the same time".
  - nirvdrum 4y ago
    Most, if not all, of the movie theaters I've been in have been fairly stationary.
  - Zigurd 4y ago
    Stadiums are actually challenging problems for mobile network builders. That's tens of thousands of people. 300 people in a passing airplane are not a problem. Computers are fast. 3MPH, or 300MPH no longer matters to mobile networks until you actually overwhelm the number of calls/connections you can pack into one place's infrastructure.
    - squeaky-clean 4y ago
      I used to live a few blocks from the AA Arena in Miami. I could always tell when a Heat game had just finished because my cell reception would drop to 1 bar or lose connection altogether. Then a few seconds later you'd hear the crowd of people reaching the parking lot right by my building.
  - giantrobot 4y ago
    Ideally mobile devices in theaters, malls, and stadiums aren't traveling at hundreds of miles an hour with a vantage such that they're in range of multiple towers simultaneously. It used to be (and maybe still is with 5G) that adjacent cells used different channel pairs. That way a handset at the edge of cell A could talk to both cell A and B to negotiate a handoff. Handoffs can happen pretty quickly. If cells A and F are on the same channel pair and a handset can see both towers the tower the handset is not talking to just has a higher noise floor. It's like in an apartment if the next unit over is on the same WiFi channel. You'll note that in older generation cell systems theaters, malls, and stadiums were terrible places for cell signals. Now many have micro/nano cells that cover much smaller areas to deal with congestion. Handsets reduce their output power when the received signal strength is better. So a handset will readily talk to a microcell at a stadium rather than try to talk to a tower further away (with a worse signal). But for planes, hundreds of passengers hitting dozens of towers simultaneously on the same channel pairs would be rough on switching. Carriers need to know where in the network to route messages to handsets. If a handset is handing off to multiple towers quickly or worse hopping seemingly randomly to towers as a jet flies over it'll be difficult to keep it connected. Multiple that by thousands of people in the air at any given time. Areas near busy airports would have absurdly unreliable connections for people in the air and on the ground.
- seanp2k2 4y ago
  US resident here. What is a train? Those things that move cows, oil, and cars across those rusty bits of metal? I don't think those are suitable for human transportation.
  - Nanana909 4y ago
    Can we avoid this here and at least have one website where we focus on the technicals and problem being discussed vs. the Americans’ interjecting their current complaints?
  - 8note 4y ago
    Trains are what keep groceries on your shelves. They almost had general strike last week because the drivers only have 5 days a year not working. No weekends, no sick days, etc.
    - yjftsjthsd-h 4y ago
      >> I don't think those are suitable for human transportation. > Trains are what keep groceries on your shelves. They almost had general strike last week because the drivers only have 5 days a year not working. No weekends, no sick days, etc. Are you trying to disagree? That sounds extremely human-hostile.
  - SgtBastard 4y ago
    If this were a thread on ever declining US education outcomes, this comment would be relevant. Please, just don’t.
  - yjftsjthsd-h 4y ago
    Dude, faux ignorance is rude and anti-conducive to useful conversation; please don't. (Unless, of course, you're sincerely unaware of trains being a widely used mode of transportation even in the States, in which case you're not rude but you should go ask Google to inform yourself.)
- deleted 4y ago
  [deleted]
- smileysteve 4y ago
  Line of sight and curvature of the earth. At 20 miles out, a device on the ground starts losing line of sight, at 20 miles out, a device on an airplane starts receiving horizontal line of sight.
  - ncmncm 4y ago
    This. Aloft, your phone sees many, many towers.
- lloeki 4y ago
  Doubly doesn't track as airplane mode is often required during takeoff and landing, which barring controlled or uncontrolled flight into terrain usually happens at the airport, where you and the so many folks taking the same airplane as well as several other airplanes are not required to take their cell phone off as a courtesy to operators. I can get the EM interference angle just fine, which stays (or stayed until recently) in place as a vestigial CYA rule of a time when cell phones were crude enough to be able to produce a spark which is what makes gas stations display a "no cellphone" sign to this day because back then it could ignite gasoline vapour.
- crazygringo 4y ago
  Most trains only go a tenth the speed of planes. And frequently much slower than that if they're making a lot of stops.
- jsjohnst 4y ago
  Trains aren’t traveling at 400-700 mph ground speed. At best they might be doing 225mph. The rate you pass by towers is thus lower. Trains also have trees, hills, buildings, earth curvature, etc obstructing how many towers your phone can see. Planes generally have a clear LOS to the tower over a significantly larger area because of the altitude. If the radiation pattern of the tower wasn’t the shape that it is, the problem would be even worse in fact.
deleted 4y ago
[deleted]
tsujamin 4y ago
Although there have been some legitimate concerns raised about some 5G bands edging into altitude sensors https://www.icao.int/safety/FSMP/MeetingDocs/FSMP%20WG11/IP/FSMP-WG11-IP08_ICAO%20Flight%20Operations%20Panel%20and%20IATA%20%20IFALPA%205G%20problem%20statement.pdf https://www.icao.int/safety/FSMP/MeetingDocs/FSMP%20WG11/IP/...
- samdcbu 4y ago
  TLDR; the aviation industry had a decent technical study done on radio altimeter interference from 5G and the FCC determined it didn’t show radio altimeter interference from 5G was likely. Then an aggregated summary of that technical data was shared with an aviation industry group (whose members include radio altimeter manufacturers), and that group used the aggregated data to claim any 5G use would likely lead to catastrophic crashes and multiple fatalities. As a private pilot and software engineer interested in spectrum policy, I’ve been following this closely for years as it’s wound it’s way through the FAA. I have yet to see any convincing, reproducible evidence that any radio altimeters that are operating within specification (filtering out all signal below 4.2 GHz) have malfunctioned due to interference from 5G cellular signals. The one thing the FAA and airline industry claim as evidence is a study by an industry group (Radio Technical Committee for Aeronautics), whose members include radio altimeter manufacturers who would benefit from large retrofits/upgrades. The RTCA didn’t actually do any of their own testing, they received aggregated data from AVSI, a Texas A&M aerospace research group, which had done a study in 2019 on radio altimeters interference. In 2020 the FCC determined that AVSI study “does not demonstrate that harmful interference would likely result under reasonable scenarios (or even reasonably 'foreseeable' scenarios to use the parlance of AVSI)”. Then, two years later when the FAA went to the NTIA (National Telecommunications and Information Administration), which is the agency tasked with managing federal spectrum and agency spectrum disputes, and demanded they stop the FCC from letting carriers turn on networks in the C-band, the NTIA refused because its own technical experts had already evaluated the technical data that RTCA used as evidence that any 5G use of 3.7 GHz - 3.98 GHz band would cause interference severe enough to cause a catastrophic crash resulting hull loss. Also, when this whole fiasco unfolded neither Verizon or AT&T had spectrum even close to the radio altimeters band. Of the C-band spectrum (3.7 GHz to 3.98 GHz) that was auctioned off a few years ago, only Block A which is between 3.7 GHz and 3.8 GHz was being used. So in addition to the existing, and potentially larger than technically required, 220 MHz guard band between 4.2 GHz (where radio altimeters start) and 3.98 GHz, when the airlines were threatening to cancel service to the US and the FAA was waging a PR war against the FCC the spectrum in question was 3.7 GHz - 3.8 GHz. Even if Verizon and AT&T rolled out 100% of the 5G spectrum they had the ability to use in 2021, it would have meant 5G cell service was within 400 MHz of the radio altimeter spectrum. The entire allocated band for radio altimeters is only 200 MHz (4.2 GHz - 4.4 GHz). Additionally, other countries like Japan have cellular providers operating in 4.0 GHz - 4.1 GHz. Japanese aviation officials (unlike the FAA) actually configured different types of 5G equipment and radio altimeters and tested them, including to see the minimum guard band needed. They found 60 MHz was the minimum guard band needed and therefore the “standard” 100 MHz guard band would be fine. They also found you shouldn’t install 5G towers directly below the approach path of an airport, but that even high powered 5G base stations won’t interfere with radio altimeters if they are 200m away. I think by far the most comprehensive explainer for this whole saga is by Harold Feld of public knowledge, which if you’re not familiar is a nonprofit advocating for an open internet which includes white papers and FCC testimony on spectrum policy they view as beneficial the public, such as allocating more of the federal government, specifically the military’s, huge bands of essentially unused spectrum. It’s on his personal blog. https://wetmachine.com/tales-of-the-sausage-factory/what-the-eff-faa-my-insanely-long-field-guide-to-the-faa-fcc-5g-c-band-fight/ https://wetmachine.com/tales-of-the-sausage-factory/what-the...
hacym 4y ago
I don’t think that’s true, or at least how you worded it is bad. Events of thousands of people don’t make you turn off your cell phone, so it’s not because of traffic to a tower. Instead, it’s interference caused by altitude and the pinging of towers. It’s actually an FCC regulation that requires it, so it’s not a courtesy as you say.
- chimeracoder 4y ago
  > I don’t think that’s true, or at least how you worded it is bad. Events of thousands of people don’t make you turn off your cell phone, so it’s not because of traffic to a tower. First of all, if you've ever been to an event with hundreds or thousands of people (such as a parade or a rally), you'll notice that even though you have "full bars", your service is degraded beyond usability, and you'll receive text messages hours late. But in this case, the issue is that people's phones will be trying to connect to many different towers in short succession, as the plane travels.
  - hacym 4y ago
    Are you trying to tell me I’m wrong by repeating what I said? > Instead, it’s interference caused by altitude and the pinging of towers.
- NavinF 4y ago
  > It’s actually an FCC regulation that requires it I don't believe you. Regardless, I have never used airplane mode on an airplane and I never will.
  - samdcbu 4y ago
    In 2013 the FCC started a regulatory preceding to evaluate allowing the use of mobile phones on airplanes, because currently there is an FCC regulation prohibiting cellular mobile phone use while a plane is in the air. in 2013 the FCC also said there were no technical reasons to prohibit their use in flight. But the preceding was ended in 2020 with no rule-making because of opposition from pilots and flight attendants.
madrox 4y ago
I once forgot to put my cell phone in airplane mode during a flight from London to SFO (and didn't use my phone during the flight). I was rather alarmed to see a flood of text messages from my carrier welcoming me to Iceland, Canada, and the US upon my landing.
- capableweb 4y ago
  That sounds... Improbable. When you were passing over Iceland you must have been far too far above the antennas to receive any sort of signal, unless it landed there on the way across the ocean?
  - mtnGoat 4y ago
    Definitely possible, 100%. Can confirm getting texts at 25k feet while not in airplane mode. I was on a flight from JFK->SEA and got welcome to Canada texts above Toronto area.
    - mmmpop 4y ago
      I too have gotten similar sorts of texts on my last trans-Atlantic flight from DIA to Frankfurt.
  - rootusrootus 4y ago
    Can't speak for Iceland specifically, but can confirm that if you fly from Seattle or Portland down to SFO, you follow a corridor of fairly strong mobile coverage most all the way, and it's occasionally usable at cruising altitude for a moment here and there. Definitely enough to get text messages.
    - margalabargala 4y ago
      This is in fact the real reason that we still have the airplane mode restriction. A phone at cruising altitude can see and try to connect to a huge number of cell towers at once. Like, orders of magnitude more towers than it would be able to see even from the top of a mountain. Plus, you're constantly disconnecting from some towers and connecting to new ones. This puts a strain on the cell network systems. One person won't have a negative impact but then you multiply the problem by the number of people who fly daily.
sbf501 4y ago
I went on six flights this summer and on each one at least one person was talking on the phone during takeoff. The flight attendants didn't even say anything. I think this request has passed.
delaaxe 4y ago
What's airport mode?
Zigurd 4y ago
Re: "Rather, 300-500 cell phones all trying to contact the next cell tower..." That might have been a concern when 2.5G was cutting edge and HLR/VLR databases ran on Sun hardware of the period. Even then, hundreds of updates in a couple seconds was not a huge challenge. Like a lot of what airlines tell customers, it is a self-serving version of reality, strongly colored for airlines' convenience and deniability.
rjcjvyd77 4y ago
> At one point, when both cell phones and laptops were new, there was perhaps a risk to the airplane's electronics. There was never any risk. Someone wrote an article in the times suggesting "perhaps" and people freaked out. There has never been a single instance or study to support this claim. The entire idea airplane mode is a farce.
- bee_rider 4y ago
  Actually, a single phone can easily cause a plane to crash. Source: This is a lie but sitting behind someone on a plane who gets a call is super annoying.
- rippercushions 4y ago
  There definitely was theoretical risk with 2G-era mobile phones, which blasted considerable amounts of radiation. I was in university once doing a signal interference lab: we had set up an circuit and we're trying to induce current in it from another circuit. Suddenly the oscilloscope on the receiving end showed a couple of wild spikes, and I received a text message on my trusty Nokia 1611: apparently 900 MHz was in the sweet spot.
  - rjcjvyd77 4y ago
  - ceejayoz 4y ago
    Yeah , my car's radio used to go nutty when my old Cingular flip phone would check in with the network or get a call.
    - sgerenser 4y ago
      Yep, it was a common sound on PC speakers in the early 2000s: https://m.youtube.com/watch?v=FYjs7vsaSEw https://m.youtube.com/watch?v=FYjs7vsaSEw
      - 4y ago
rory 4y ago
Before landing on the last flight I was on, the flight attendants requested that everyone turn off their phones (even if in airplane mode) due to the weather conditions while landing. Does anyone know what purpose that could possibly serve? This was in France if that's a relevant clue.
- Gh0stRAT 4y ago
  Probably because the pilots were going to be flying an IFR approach. (flying on just instruments through low visibility near the ground, a worst-case scenario for interference being able to cause a fatal crash)
- ktta 4y ago
  The France clue actually contradicts my guess, because I'm guessing that was an Airbus? Anyways, he's one theory: Boeing has an issue where its radio altimeters are affected by C-band 5G transmissions. I believe maybe the pilots were relying more on the precision of the altimeter because their vision was impaired due to the bad weather? The whole 'turn off phones' instruction could be because people would follow the unusual request to turn off their phones instead of just telling them to put it in airplane mode (which is so common that some people just don't bother)
  - rory 4y ago
    I'm pretty ignorant of airplane models, Air France flight but it was a large plane so may have been a Boeing 777.
    - atlasunshrugged 4y ago
      I think they meant because it's Air France and the EU generally tries to support Airbus (based in Europe) rather than Boeing (based in the U.S.) it seems likely that it is an Airbus aircraft
      - rory 4y ago
        I understand-- I looked it up, and although they're only buying Airbus going forward, most of their 10-across fleet is still 777: https://en.wikipedia.org/wiki/Air_France_fleet https://en.wikipedia.org/wiki/Air_France_fleet
rzimmerman 4y ago
Switching your phone transmitter off is technically required by FCC regulations: https://www.ecfr.gov/current/title-47/chapter-I/subchapter-B/part-22/subpart-H/section-22.925 https://www.ecfr.gov/current/title-47/chapter-I/subchapter-B... Realistically there isn't an issue with leaving a cell phone on and out of airplane mode going purely based on how many people forget or ignore the directions everyday and how infrequently there are problems. But I'll make two points: The idea that a cell phone transmitter can interfere with an airplane is by no means outrageous. Sure, a modern iPhone/Pixel/whatever has to meet certain emissions and interference standards. And modern airliners are designed with some interference rejection in mind. And ancient airliners from the 70s don't rely on a lot of electronic systems at all. As for airplanes designed in the 90s, well it's not silly to ask whether 200 people with 1W transmitters would interfere with the electronic systems. A properly functioning compliant phone shouldn't, but there's still some risk. Incidents do happen, though they are generally minor. I was on an airplane that had to abort a landing and go-around because they couldn't hear the tower over cellphone interference (voice comms are analog). Obviously no one died, but we were still delayed a bit. It probably makes sense to relax the rules, but it is incredibly frustrating to see the attitude of "if they don't force me to turn it off it must be OK". The FCC requires you to turn off transmitters to avoid interference. The airline asks you to do so for the same reason. Experts in the field (myself included) are telling you there's a small risk and you should hit the airplane mode button. There's zero benefit to keeping your cellular service active in flight at all. But everyone's seen some article on Facebook (or in this case inverse.com) that says maybe there's a big conspiracy and everyone's lying to them. So they take a risk (albeit an extremely small one) with the lives of 200 other people. For no gain at all. So do whatever you want, there's nothing I can do about human nature, but believe me when I tell you there's no government conspiracy to make you press the little airplane button funded by the cell phone companies. Yeah, the risk is probably negligible - it's just really hard to prove it and easier to make a small ask of passengers.
- johnwalkr 4y ago
  A few airlines (Etihad is one that comes to mind) operate mini cells on the plan and you can roam on a local 4G network and makes calls/use data. If I recall correctly it’s switched off on takeoff and landing but you can definitely use your phone on these flights.
crystaln 4y ago
The term airplane mode will persist as an anachronism forever. Some day we will have to explain to our grandchildren why disabling networks has anything to do with airplanes.
- imwillofficial 4y ago
  “Grandpa, what’s an airplane?” “Well Nancy, before instant interdimensional travel…”
  - cercatrova 4y ago
    Imagine physically traveling through a medium. I only transmit my bits instantaneously and get reconstructed on the other side.
- spideymans 4y ago
  My most frequent use of the airplane mode, is when I go underground on metro systems, which I find pretty ironic. (Without Airplane Mode, the phone will keep trying to connect to cellular towers, which just makes the network experience unstable) Perhaps "Underground Mode" would be more suitable in a modern context /s
  - smabie 4y ago
    Isn't an unstable network experience better than no network experience?
    - rsync 4y ago
      "Isn't an unstable network experience better than no network experience?" Yes, you would think ... but that is not the case. QA and design of modern mobile apps and software - and even devices and appliances - neglects the testing of bad network connectivity. Both my physical Sonos devices and, for instance, the apple-provided podcasts app, can handle being fully offline reasonably well. On the other hand, if you start dropping ~50% of packets they lose their mind and (in the case of Apples podcast app) freeze or crash.
jpmattia 4y ago
> Rather, 300-500 cell phones all trying to contact the next cell tower, multiple times per minute, would wreak havoc on cell service. I'm probably being a simpleton, but this sounds like inadequate firmware to me. At the very least: Airtags have GPS, so shut them off when they are at $ALTITUDE.
- simlevesque 4y ago
  I mean, let's think this all can work. You turn it off at $ALTITUDE. When do you turn them on ? There's no button and it is powered off.
- tengwar2 4y ago
  They don't appear to have GPS. Rather they contact local Apple devices over Bluetooth, and those devices know where they are. But then they don't have cellular access either, so this discussion is moot.
deleted 4y ago
[deleted]
dehrmann 4y ago
Users benefit, too. You phone uses a lot more power when trying to connect to all those towers.
nraynaud 4y ago
I’m a bit skeptical, bullet trains swamp towers too, they just put more towers along the tracks.
- fomine3 4y ago
  For bullet trains, it's worth to invest for train users. For airplane, it isn't.
btbuildem 4y ago
If there was ever a shade of a possibility that a cellphone or other electronic device could interfere with the operation of an aircraft, they'd never even let you take anything like that onboard. The whole "turn off your devices" thing is more about validating compliance and making people pay attention during the most incident-prone times of flight (takeoff and landing)

alexnewman 4y ago

luckily this happens all the time since people often forget. i know i do.

sigwinch28 4y ago

> Note that the reason for airport mode is a courtesy to cell-phone carriers. This doesn’t track. What about trains?

joecot 4y ago
Trains move significantly slower than planes. They're also on the ground, mostly below the towers, while planes are in the air, moving very fast, with multiple towers in line of sight.
scandinavian 4y ago
It doesn't track in any way. In the airport there's small cells or femtocells by the operators. In the air, the only cells you can reach are the one pointing upwards. Also, they don't really ask for airplane mode anymore, at least not when I'm flying.
gnfargbl 4y ago
The cell tower network is designed to cope with devices located on the surface of the planet, i.e. where the geometry between the handsets and the tower is roughly two-dimensional. I am also unconvinced that handsets on aeroplanes are really a problem for the network, but trains aren't the counterexample you're making them out to be.
- Kye 4y ago
  Flight patterns are also pretty consistent. Tower planners have probably given some thought to it.
  - afavour 4y ago
    That doesn't address the 2 vs 3D problem the person you’re replying to outlined.
  - samdcbu 4y ago
    Cell towers are designed for terrestrial users because their radios aren’t pointed at the sky. Gogo provides inflight Wi-Fi in the US through its ground based towers and all the antennas are pointed at the sky :) Flights (at least in the US) fly roughly a direct route, but ATC spaces out planes and small weather diversions are common. So it’s more like a band of coverage needed between cities. Also, the combinatorics of considering every US city pair that currently or has previously had commercial service between gets long. Then you would have to consider every route that an airline in the future may offer, even just seasonally. Then if you calculated the optimal route between each pair and figured out the width of the cellular coverage at 30,000 ft from a single cell tower below, I don’t think it would be possible to offer service to every domestic flight in the US without achieving complete coverage of the US. China on the other hand has a limited number of very narrow flight corridors that all commercial aviation is restricted to because the majority of the airspace is government controlled. That’s the only nation I can think of that would have enough air traffic to justify terrestrial tower installation but whose domestic flights are confined to a such a small part of the airspace that it would be possible to provide service to all domestic flights without achieving coverage of all Chinese airspace.
nostrademons 4y ago
You're supposed to put your phone on airplane mode in a train or subway too, but most people don't: https://pocketnow.com/airplane-mode/ https://pocketnow.com/airplane-mode/ The problem is significantly lessened for trains vs. planes though because you're traveling an order of magnitude slower and hence you switch cells an order of magnitude less frequently. Also many commuter rails run alongside major highways or boulevards, where the cell systems are built assuming lots of cell handoffs at roughly highway speeds. If enough people used high-speed rail to overwhelm the cell system we'd probably see announcements to put phones in airplane mode there too, but very few folks will travel long distances at high speeds on a train.
- Bluecobra 4y ago
  That article sounds like a bunch of hogwash to me. The CTA in Chicago specifically has cell phone infrastructure in the subway lines, and that predates that article. https://www.transitchicago.com/cta-to-bring-4g-wireless-service-to-subways/ https://www.transitchicago.com/cta-to-bring-4g-wireless-serv...
- hocuspocus 4y ago
  > You're supposed to put your phone on airplane mode in a train or subway too, That's a pretty insane claim in most of the world. Lots of people expect and enjoy full coverage on train or subway rides. I work at a carrier and the signal strength and cell capacity on trains are part of the top metrics we use to benchmark the quality of our network and the customer experience.
  - brewdad 4y ago
    > You're supposed to put your phone on airplane mode in a train or subway too, Why would you be expected to do this when we don't require drivers to put their phones in airplane mode? I get that US trains are slow compared to other parts of the world, but does the Autobahn require airplane mode? Doubtful since my German car happily connects to my phone in multiple ways.
  - danw1979 4y ago
    >> You're supposed to put your phone on airplane mode in a train or subway too, > That's a pretty insane claim in most of the world. So is this: > but very few folks will travel long distances at high speeds on a train.
henrikeh 4y ago
Cell phone cells are (ideally) shaped to account for the expected pattern of how handover will occur. Along roads and train lines, the cells are (at least in GSM) supposed to be tailored to allow for easy routing and handover as the devices travels in the direction of the way. While I have never read anything concretely analyzing the handover pattern of devices on airplanes, I would expect that since a very large number of cells are almost equally visible/equal signal strength, the network would have to frequently handover the device from one cell to another. The handover process is, for voice traffic, very resource intense. (in GSM) it involves duplication of traffic to the neighboring cell and a lot of coordination. I think that could be the reason for why mobile operators find airplane-borne devices annoying.
dsr_ 4y ago
Line-of-sight. If you're 4-5 miles up with no blockers except the aircraft skin, you get to confuse a lot of towers at once.
- hombre_fatal 4y ago
  Must not be very much of an issue since there’s basically zero messaging around what airplane mode is for. Not once has any of my carriers even said “please turn on airplane mode to help the network”. Instead it’s an in-passing recommendation made by air stewardesses so boilerplate it feels like superstition. I wonder what the actual impact is and how that relates to the low effort messaging around airplane mode.
xani_ 4y ago
Compare the speeds of both modes of transport
enumjorge 4y ago
And movie theaters, malls, stadiums. Maybe I’m missing something?
- matthewmacleod 4y ago
  If you're in a stadium travelling at 600mph, you have a heck of a problem! I think the challenge isn't so much "lots of people in one place" as "lots of people travelling extremely fast with line-of-sight to hundreds of cellular towers at the same time".
- nirvdrum 4y ago
  Most, if not all, of the movie theaters I've been in have been fairly stationary.
- Zigurd 4y ago
  Stadiums are actually challenging problems for mobile network builders. That's tens of thousands of people. 300 people in a passing airplane are not a problem. Computers are fast. 3MPH, or 300MPH no longer matters to mobile networks until you actually overwhelm the number of calls/connections you can pack into one place's infrastructure.
  - squeaky-clean 4y ago
    I used to live a few blocks from the AA Arena in Miami. I could always tell when a Heat game had just finished because my cell reception would drop to 1 bar or lose connection altogether. Then a few seconds later you'd hear the crowd of people reaching the parking lot right by my building.
- giantrobot 4y ago
  Ideally mobile devices in theaters, malls, and stadiums aren't traveling at hundreds of miles an hour with a vantage such that they're in range of multiple towers simultaneously. It used to be (and maybe still is with 5G) that adjacent cells used different channel pairs. That way a handset at the edge of cell A could talk to both cell A and B to negotiate a handoff. Handoffs can happen pretty quickly. If cells A and F are on the same channel pair and a handset can see both towers the tower the handset is not talking to just has a higher noise floor. It's like in an apartment if the next unit over is on the same WiFi channel. You'll note that in older generation cell systems theaters, malls, and stadiums were terrible places for cell signals. Now many have micro/nano cells that cover much smaller areas to deal with congestion. Handsets reduce their output power when the received signal strength is better. So a handset will readily talk to a microcell at a stadium rather than try to talk to a tower further away (with a worse signal). But for planes, hundreds of passengers hitting dozens of towers simultaneously on the same channel pairs would be rough on switching. Carriers need to know where in the network to route messages to handsets. If a handset is handing off to multiple towers quickly or worse hopping seemingly randomly to towers as a jet flies over it'll be difficult to keep it connected. Multiple that by thousands of people in the air at any given time. Areas near busy airports would have absurdly unreliable connections for people in the air and on the ground.
seanp2k2 4y ago
US resident here. What is a train? Those things that move cows, oil, and cars across those rusty bits of metal? I don't think those are suitable for human transportation.
- Nanana909 4y ago
  Can we avoid this here and at least have one website where we focus on the technicals and problem being discussed vs. the Americans’ interjecting their current complaints?
- 8note 4y ago
  Trains are what keep groceries on your shelves. They almost had general strike last week because the drivers only have 5 days a year not working. No weekends, no sick days, etc.
  - yjftsjthsd-h 4y ago
    >> I don't think those are suitable for human transportation. > Trains are what keep groceries on your shelves. They almost had general strike last week because the drivers only have 5 days a year not working. No weekends, no sick days, etc. Are you trying to disagree? That sounds extremely human-hostile.
- SgtBastard 4y ago
  If this were a thread on ever declining US education outcomes, this comment would be relevant. Please, just don’t.
- yjftsjthsd-h 4y ago
  Dude, faux ignorance is rude and anti-conducive to useful conversation; please don't. (Unless, of course, you're sincerely unaware of trains being a widely used mode of transportation even in the States, in which case you're not rude but you should go ask Google to inform yourself.)
deleted 4y ago
[deleted]
smileysteve 4y ago
Line of sight and curvature of the earth. At 20 miles out, a device on the ground starts losing line of sight, at 20 miles out, a device on an airplane starts receiving horizontal line of sight.
- ncmncm 4y ago
  This. Aloft, your phone sees many, many towers.
lloeki 4y ago
Doubly doesn't track as airplane mode is often required during takeoff and landing, which barring controlled or uncontrolled flight into terrain usually happens at the airport, where you and the so many folks taking the same airplane as well as several other airplanes are not required to take their cell phone off as a courtesy to operators. I can get the EM interference angle just fine, which stays (or stayed until recently) in place as a vestigial CYA rule of a time when cell phones were crude enough to be able to produce a spark which is what makes gas stations display a "no cellphone" sign to this day because back then it could ignite gasoline vapour.
crazygringo 4y ago
Most trains only go a tenth the speed of planes. And frequently much slower than that if they're making a lot of stops.
jsjohnst 4y ago
Trains aren’t traveling at 400-700 mph ground speed. At best they might be doing 225mph. The rate you pass by towers is thus lower. Trains also have trees, hills, buildings, earth curvature, etc obstructing how many towers your phone can see. Planes generally have a clear LOS to the tower over a significantly larger area because of the altitude. If the radiation pattern of the tower wasn’t the shape that it is, the problem would be even worse in fact.

deleted 4y ago

[deleted]

tsujamin 4y ago

Although there have been some legitimate concerns raised about some 5G bands edging into altitude sensors https://www.icao.int/safety/FSMP/MeetingDocs/FSMP%20WG11/IP/FSMP-WG11-IP08_ICAO%20Flight%20Operations%20Panel%20and%20IATA%20%20IFALPA%205G%20problem%20statement.pdf https://www.icao.int/safety/FSMP/MeetingDocs/FSMP%20WG11/IP/...

samdcbu 4y ago
TLDR; the aviation industry had a decent technical study done on radio altimeter interference from 5G and the FCC determined it didn’t show radio altimeter interference from 5G was likely. Then an aggregated summary of that technical data was shared with an aviation industry group (whose members include radio altimeter manufacturers), and that group used the aggregated data to claim any 5G use would likely lead to catastrophic crashes and multiple fatalities. As a private pilot and software engineer interested in spectrum policy, I’ve been following this closely for years as it’s wound it’s way through the FAA. I have yet to see any convincing, reproducible evidence that any radio altimeters that are operating within specification (filtering out all signal below 4.2 GHz) have malfunctioned due to interference from 5G cellular signals. The one thing the FAA and airline industry claim as evidence is a study by an industry group (Radio Technical Committee for Aeronautics), whose members include radio altimeter manufacturers who would benefit from large retrofits/upgrades. The RTCA didn’t actually do any of their own testing, they received aggregated data from AVSI, a Texas A&M aerospace research group, which had done a study in 2019 on radio altimeters interference. In 2020 the FCC determined that AVSI study “does not demonstrate that harmful interference would likely result under reasonable scenarios (or even reasonably 'foreseeable' scenarios to use the parlance of AVSI)”. Then, two years later when the FAA went to the NTIA (National Telecommunications and Information Administration), which is the agency tasked with managing federal spectrum and agency spectrum disputes, and demanded they stop the FCC from letting carriers turn on networks in the C-band, the NTIA refused because its own technical experts had already evaluated the technical data that RTCA used as evidence that any 5G use of 3.7 GHz - 3.98 GHz band would cause interference severe enough to cause a catastrophic crash resulting hull loss. Also, when this whole fiasco unfolded neither Verizon or AT&T had spectrum even close to the radio altimeters band. Of the C-band spectrum (3.7 GHz to 3.98 GHz) that was auctioned off a few years ago, only Block A which is between 3.7 GHz and 3.8 GHz was being used. So in addition to the existing, and potentially larger than technically required, 220 MHz guard band between 4.2 GHz (where radio altimeters start) and 3.98 GHz, when the airlines were threatening to cancel service to the US and the FAA was waging a PR war against the FCC the spectrum in question was 3.7 GHz - 3.8 GHz. Even if Verizon and AT&T rolled out 100% of the 5G spectrum they had the ability to use in 2021, it would have meant 5G cell service was within 400 MHz of the radio altimeter spectrum. The entire allocated band for radio altimeters is only 200 MHz (4.2 GHz - 4.4 GHz). Additionally, other countries like Japan have cellular providers operating in 4.0 GHz - 4.1 GHz. Japanese aviation officials (unlike the FAA) actually configured different types of 5G equipment and radio altimeters and tested them, including to see the minimum guard band needed. They found 60 MHz was the minimum guard band needed and therefore the “standard” 100 MHz guard band would be fine. They also found you shouldn’t install 5G towers directly below the approach path of an airport, but that even high powered 5G base stations won’t interfere with radio altimeters if they are 200m away. I think by far the most comprehensive explainer for this whole saga is by Harold Feld of public knowledge, which if you’re not familiar is a nonprofit advocating for an open internet which includes white papers and FCC testimony on spectrum policy they view as beneficial the public, such as allocating more of the federal government, specifically the military’s, huge bands of essentially unused spectrum. It’s on his personal blog. https://wetmachine.com/tales-of-the-sausage-factory/what-the-eff-faa-my-insanely-long-field-guide-to-the-faa-fcc-5g-c-band-fight/ https://wetmachine.com/tales-of-the-sausage-factory/what-the...

hacym 4y ago

I don’t think that’s true, or at least how you worded it is bad. Events of thousands of people don’t make you turn off your cell phone, so it’s not because of traffic to a tower. Instead, it’s interference caused by altitude and the pinging of towers. It’s actually an FCC regulation that requires it, so it’s not a courtesy as you say.

chimeracoder 4y ago
> I don’t think that’s true, or at least how you worded it is bad. Events of thousands of people don’t make you turn off your cell phone, so it’s not because of traffic to a tower. First of all, if you've ever been to an event with hundreds or thousands of people (such as a parade or a rally), you'll notice that even though you have "full bars", your service is degraded beyond usability, and you'll receive text messages hours late. But in this case, the issue is that people's phones will be trying to connect to many different towers in short succession, as the plane travels.
- hacym 4y ago
  Are you trying to tell me I’m wrong by repeating what I said? > Instead, it’s interference caused by altitude and the pinging of towers.
NavinF 4y ago
> It’s actually an FCC regulation that requires it I don't believe you. Regardless, I have never used airplane mode on an airplane and I never will.
- samdcbu 4y ago
  In 2013 the FCC started a regulatory preceding to evaluate allowing the use of mobile phones on airplanes, because currently there is an FCC regulation prohibiting cellular mobile phone use while a plane is in the air. in 2013 the FCC also said there were no technical reasons to prohibit their use in flight. But the preceding was ended in 2020 with no rule-making because of opposition from pilots and flight attendants.

madrox 4y ago

I once forgot to put my cell phone in airplane mode during a flight from London to SFO (and didn't use my phone during the flight). I was rather alarmed to see a flood of text messages from my carrier welcoming me to Iceland, Canada, and the US upon my landing.

capableweb 4y ago
That sounds... Improbable. When you were passing over Iceland you must have been far too far above the antennas to receive any sort of signal, unless it landed there on the way across the ocean?
- mtnGoat 4y ago
  Definitely possible, 100%. Can confirm getting texts at 25k feet while not in airplane mode. I was on a flight from JFK->SEA and got welcome to Canada texts above Toronto area.
  - mmmpop 4y ago
    I too have gotten similar sorts of texts on my last trans-Atlantic flight from DIA to Frankfurt.
- rootusrootus 4y ago
  Can't speak for Iceland specifically, but can confirm that if you fly from Seattle or Portland down to SFO, you follow a corridor of fairly strong mobile coverage most all the way, and it's occasionally usable at cruising altitude for a moment here and there. Definitely enough to get text messages.
  - margalabargala 4y ago
    This is in fact the real reason that we still have the airplane mode restriction. A phone at cruising altitude can see and try to connect to a huge number of cell towers at once. Like, orders of magnitude more towers than it would be able to see even from the top of a mountain. Plus, you're constantly disconnecting from some towers and connecting to new ones. This puts a strain on the cell network systems. One person won't have a negative impact but then you multiply the problem by the number of people who fly daily.

sbf501 4y ago

I went on six flights this summer and on each one at least one person was talking on the phone during takeoff. The flight attendants didn't even say anything. I think this request has passed.

delaaxe 4y ago

What's airport mode?

Zigurd 4y ago

Re: "Rather, 300-500 cell phones all trying to contact the next cell tower..." That might have been a concern when 2.5G was cutting edge and HLR/VLR databases ran on Sun hardware of the period. Even then, hundreds of updates in a couple seconds was not a huge challenge. Like a lot of what airlines tell customers, it is a self-serving version of reality, strongly colored for airlines' convenience and deniability.

rjcjvyd77 4y ago

> At one point, when both cell phones and laptops were new, there was perhaps a risk to the airplane's electronics. There was never any risk. Someone wrote an article in the times suggesting "perhaps" and people freaked out. There has never been a single instance or study to support this claim. The entire idea airplane mode is a farce.

bee_rider 4y ago
Actually, a single phone can easily cause a plane to crash. Source: This is a lie but sitting behind someone on a plane who gets a call is super annoying.
rippercushions 4y ago
There definitely was theoretical risk with 2G-era mobile phones, which blasted considerable amounts of radiation. I was in university once doing a signal interference lab: we had set up an circuit and we're trying to induce current in it from another circuit. Suddenly the oscilloscope on the receiving end showed a couple of wild spikes, and I received a text message on my trusty Nokia 1611: apparently 900 MHz was in the sweet spot.
- rjcjvyd77 4y ago
- ceejayoz 4y ago
  Yeah , my car's radio used to go nutty when my old Cingular flip phone would check in with the network or get a call.
  - sgerenser 4y ago
    Yep, it was a common sound on PC speakers in the early 2000s: https://m.youtube.com/watch?v=FYjs7vsaSEw https://m.youtube.com/watch?v=FYjs7vsaSEw
    - 4y ago

rory 4y ago

Before landing on the last flight I was on, the flight attendants requested that everyone turn off their phones (even if in airplane mode) due to the weather conditions while landing. Does anyone know what purpose that could possibly serve? This was in France if that's a relevant clue.

Gh0stRAT 4y ago
Probably because the pilots were going to be flying an IFR approach. (flying on just instruments through low visibility near the ground, a worst-case scenario for interference being able to cause a fatal crash)
ktta 4y ago
The France clue actually contradicts my guess, because I'm guessing that was an Airbus? Anyways, he's one theory: Boeing has an issue where its radio altimeters are affected by C-band 5G transmissions. I believe maybe the pilots were relying more on the precision of the altimeter because their vision was impaired due to the bad weather? The whole 'turn off phones' instruction could be because people would follow the unusual request to turn off their phones instead of just telling them to put it in airplane mode (which is so common that some people just don't bother)
- rory 4y ago
  I'm pretty ignorant of airplane models, Air France flight but it was a large plane so may have been a Boeing 777.
  - atlasunshrugged 4y ago
    I think they meant because it's Air France and the EU generally tries to support Airbus (based in Europe) rather than Boeing (based in the U.S.) it seems likely that it is an Airbus aircraft
    - rory 4y ago
      I understand-- I looked it up, and although they're only buying Airbus going forward, most of their 10-across fleet is still 777: https://en.wikipedia.org/wiki/Air_France_fleet https://en.wikipedia.org/wiki/Air_France_fleet

rzimmerman 4y ago

Switching your phone transmitter off is technically required by FCC regulations: https://www.ecfr.gov/current/title-47/chapter-I/subchapter-B/part-22/subpart-H/section-22.925 https://www.ecfr.gov/current/title-47/chapter-I/subchapter-B... Realistically there isn't an issue with leaving a cell phone on and out of airplane mode going purely based on how many people forget or ignore the directions everyday and how infrequently there are problems. But I'll make two points: The idea that a cell phone transmitter can interfere with an airplane is by no means outrageous. Sure, a modern iPhone/Pixel/whatever has to meet certain emissions and interference standards. And modern airliners are designed with some interference rejection in mind. And ancient airliners from the 70s don't rely on a lot of electronic systems at all. As for airplanes designed in the 90s, well it's not silly to ask whether 200 people with 1W transmitters would interfere with the electronic systems. A properly functioning compliant phone shouldn't, but there's still some risk. Incidents do happen, though they are generally minor. I was on an airplane that had to abort a landing and go-around because they couldn't hear the tower over cellphone interference (voice comms are analog). Obviously no one died, but we were still delayed a bit. It probably makes sense to relax the rules, but it is incredibly frustrating to see the attitude of "if they don't force me to turn it off it must be OK". The FCC requires you to turn off transmitters to avoid interference. The airline asks you to do so for the same reason. Experts in the field (myself included) are telling you there's a small risk and you should hit the airplane mode button. There's zero benefit to keeping your cellular service active in flight at all. But everyone's seen some article on Facebook (or in this case inverse.com) that says maybe there's a big conspiracy and everyone's lying to them. So they take a risk (albeit an extremely small one) with the lives of 200 other people. For no gain at all. So do whatever you want, there's nothing I can do about human nature, but believe me when I tell you there's no government conspiracy to make you press the little airplane button funded by the cell phone companies. Yeah, the risk is probably negligible - it's just really hard to prove it and easier to make a small ask of passengers.

johnwalkr 4y ago
A few airlines (Etihad is one that comes to mind) operate mini cells on the plan and you can roam on a local 4G network and makes calls/use data. If I recall correctly it’s switched off on takeoff and landing but you can definitely use your phone on these flights.

crystaln 4y ago

The term airplane mode will persist as an anachronism forever. Some day we will have to explain to our grandchildren why disabling networks has anything to do with airplanes.

imwillofficial 4y ago
“Grandpa, what’s an airplane?” “Well Nancy, before instant interdimensional travel…”
- cercatrova 4y ago
  Imagine physically traveling through a medium. I only transmit my bits instantaneously and get reconstructed on the other side.
spideymans 4y ago
My most frequent use of the airplane mode, is when I go underground on metro systems, which I find pretty ironic. (Without Airplane Mode, the phone will keep trying to connect to cellular towers, which just makes the network experience unstable) Perhaps "Underground Mode" would be more suitable in a modern context /s
- smabie 4y ago
  Isn't an unstable network experience better than no network experience?
  - rsync 4y ago
    "Isn't an unstable network experience better than no network experience?" Yes, you would think ... but that is not the case. QA and design of modern mobile apps and software - and even devices and appliances - neglects the testing of bad network connectivity. Both my physical Sonos devices and, for instance, the apple-provided podcasts app, can handle being fully offline reasonably well. On the other hand, if you start dropping ~50% of packets they lose their mind and (in the case of Apples podcast app) freeze or crash.

jpmattia 4y ago

> Rather, 300-500 cell phones all trying to contact the next cell tower, multiple times per minute, would wreak havoc on cell service. I'm probably being a simpleton, but this sounds like inadequate firmware to me. At the very least: Airtags have GPS, so shut them off when they are at $ALTITUDE.

simlevesque 4y ago
I mean, let's think this all can work. You turn it off at $ALTITUDE. When do you turn them on ? There's no button and it is powered off.
tengwar2 4y ago
They don't appear to have GPS. Rather they contact local Apple devices over Bluetooth, and those devices know where they are. But then they don't have cellular access either, so this discussion is moot.

deleted 4y ago

[deleted]

dehrmann 4y ago

Users benefit, too. You phone uses a lot more power when trying to connect to all those towers.

nraynaud 4y ago

I’m a bit skeptical, bullet trains swamp towers too, they just put more towers along the tracks.

fomine3 4y ago
For bullet trains, it's worth to invest for train users. For airplane, it isn't.

btbuildem 4y ago

If there was ever a shade of a possibility that a cellphone or other electronic device could interfere with the operation of an aircraft, they'd never even let you take anything like that onboard. The whole "turn off your devices" thing is more about validating compliance and making people pay attention during the most incident-prone times of flight (takeoff and landing)