Are personal electronics (of present or recent past; e.g. cell phones, mp3 players, iPads) a risk to commercial air travel? Is the typical request to "turn off all personal electronic devices" based on any reasonable data?
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7Don't have a source for this so I'm putting it in a comment, but keep in mind the EMF the airplane experiences from e.g. space -- the electronics must be shielded for that reason alone. Therefore I find it highly unlikely that any type of consumer electronic device would have any affect on avionics. Plus there are no known cases of these devices causing a problem. (But I don't have sources so I'm not going to put this as an answer) – Billy ONeal Mar 22 '11 at 15:01
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9I'm not going to be able to give a better answer than those that has answered. But if mobile phones really was a danger to aviation do anyone actually think they would let you board with one? You can't bloody well bring water on the plane anymore... – Kit Sunde Mar 22 '11 at 17:14
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4Commenting here, because this keeps coming up in answers. Confiscation (lack thereof) is not an issue. Lots of items much more dangerous than cell phones are not confiscated (lithium batteries). Lack of confiscation does not indicate lack of risk. – Russell Steen Mar 22 '11 at 19:21
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1I remember an interview (on one of the security blogs I follow) with a TSA official, in which he states something like, "Really, we make them turn off all electronics during take-off/landing so they'll give their full attention to the flight attendants." I can't seem to find the source for this, though. – BlueRaja - Danny Pflughoeft Mar 22 '11 at 22:18
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4@Billy ONeal: EMF from space is coming from outside, like blizzards, but the plane builds a Faraday cage. Consumer electronics are inside the plane. Should make a difference, no? – user unknown Mar 23 '11 at 00:07
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2@user: Can't be a complete Faraday cage -- the avionics still need to be able to transmit and receive themselves. Most pilots would be quite unhappy if you took away their communications, transponders, VORs, DME, NDBs, GPSs, LORANs, and ILSs. ;) – Billy ONeal Mar 23 '11 at 00:36
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2@user unknown: Plus the assumption is that the cell phones actually **work** right? That implies that the skin of the plane isn't complete shielding. – Billy ONeal Mar 23 '11 at 00:45
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1Maybe the avionics work, because they have an antenna outside? – user unknown Mar 23 '11 at 00:58
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2@user unknown: The cell phone's antenna certainly isn't outside. – Billy ONeal Mar 23 '11 at 07:12
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There can be an antenna outside, connected to a repeater inside. No? I'm not sure. On the other hand, frequencies are strictly restricted to not interfere with each other. – user unknown Mar 23 '11 at 07:23
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These regulations predate mass use of cellphones. Anything with a local oscillator was restricted when I flew in the 80s, including portable radios & TV *receivers* (two way radios being obvious NO-NOs). This was not always enforced. Radio & TV receivers work by mixing the LO with the incoming signal to produce sum and difference frequencies. The difference frequency is called the IF or intermediate frequency. The rest of the device is designed to process the IF. In theory the LO on a malfunctioning and poorly shielded radio could interfere with other devices. – Paul Mar 24 '11 at 05:15
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5@user unknown: It is possible to make and receive phone calls if you turned on your cellphone inside the plane (of course while the plane is still on land and in the range of a cell tower). If a plane's body truly acted as a Faraday cage, a phone should receive no (or lowered) signal inside a plane. – Lie Ryan Mar 26 '11 at 19:32
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1I don't know. I rarely fly and I rarely phone. I just know, that in our metro system, there are repeaters, to make cell phones work under the ground, but on the other side, the trains themselves are made from metal too. I learned in school, that a car is safe in lightening, because it is a Faraday cage, but I don't know the details. Maybe the wavelength is important, relative to the window size? Well, consulting the german Wikipedia http://de.wikipedia.org/wiki/Faradayscher_K%C3%A4fig I read: In fact, a Faraday Cage blocks mobile phones, and a plane is a Faraday Cage, but ... – user unknown Mar 26 '11 at 19:50
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... but the wavelength of mobile phones is so short, that you may use your phone in cars. I didn't find such a paragraph in the english version. – user unknown Mar 26 '11 at 19:52
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Wow, has no-one addressed the "Nothing to do with RF radiation, but everything to do with having people ready to listen to instructions and to evacuate, during the most dangerous parts of the flight" argument? – Oddthinking Oct 04 '11 at 07:56
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@Oddthinking, actually that's another argument I hadn't thought of. Could you post an answer elaborating on that? – DuckMaestro Oct 04 '11 at 18:05
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1@DuckMaestro: Here's an [unreferenced web-site](http://www.askthepilot.com/chapter-5/#c5-q5) making the claim. Has anyone mentioned that cellphones on flights would be annoying to other passengers? Could be another factor. I think this question needs a summary answer that points out that it might not be as simple as one organisation making one rational decision based on one risk, with a documented rationalisation serving as a smoking gun. – Oddthinking Oct 05 '11 at 01:23
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2This may not be solid, scientific evidence, but consider this: Bearing in mind that electronic devices can be on without visibly appearing to be on, it's trivial to have one running without anyone noticing. If one could interfere with a plane's systems enough to put the passengers in danger--it was *really that easy* to crash a plane--then sometime in the last 10 years, some terrorist would have done it, or at least tried to do it, and we wouldn't be allowed to take them onto planes now. You know it's true. Therefore, personal electronic devices are harmless to aircraft systems. ;) – Mason Wheeler Feb 25 '12 at 22:17
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A related article: http://bits.blogs.nytimes.com/2013/05/09/30-percent-of-passengers-accidentally-leave-a-device-on-during-flight/ – DuckMaestro May 10 '13 at 17:53
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Related on aviation.SE: [Instrument landing: why do all electronic devices need to be shut off?](http://aviation.stackexchange.com/q/11555/755) – reirab Jan 27 '16 at 20:51
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In aviation things are considered dangerous until proven safe, rather than the other way around. So the rule isn't based on known incidents that were dangerous, but on the lack of evidence that the risks are acceptably low. – Paul Johnson Aug 23 '18 at 20:23
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From ABC News (2007):
An aviation safety database maintained by NASA shows a handful of incidents each year reported by pilots who suspected cell phones and other electronic devices had caused a problem during flight. Despite these reports, not a single air crash has been proven to be caused by the use of a cell phone onboard a plane.
John Nance, an ABC News consultant and veteran airline pilot, says there's little reason to worry about cell phones interfering with an airplane's navigational equipment. He says an airplane's electronic systems are "all heavily shielded. That means that stray signals cannot get into those systems."
The airlines can't allow cell phones to be used in flight until the technology has been proven safe. However, according to Nance, the Federal Communications Commission and the Federal Aviation Administration "have not done their job over about a 25-year period. And the airlines have quite properly said … if you're not going to tell us, then we're just going to default to the most conservative position and say we're not going to use them in the air."
Here is a study done in 2003 that concludes "Cellphones and other electronics are more of a risk than you think"
regulations already permit a wide variety of other portable electronic devices--from game machines to laptops with Wi-Fi cards--to be used in the air today. Yet our research has found that these items can interrupt the normal operation of key cockpit instruments, especially Global Positioning System (GPS) receivers, which are increasingly vital to safe landings.
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There is no smoking gun to this story: there is no definitive instance of an air accident known to have been caused by a passenger's use of an electronic device. Nonetheless, although it is impossible to say that such use has contributed to air accidents in the past, the data also make it impossible to rule it out completely.
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Consumer devices that meet FCC emission limits can exceed safe interference limits set by the FAA for avionics, because the FCC and the FAA do not harmonize their regulations.
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At present, we believe that passenger use of electronics on board commercial aircraft should continue to be limited and that passengers should not be allowed to operate intentionally radiating devices such as cellphones and wireless computer equipment during critical stages of flight.
Let's presume there is a 0.01% chance that cell phones can cause a crash. Worldwide there will surely be more than 10.000 flights per day. So even with such a low percentage it would mean at least one crash per day. Looking at it this way I can understand the ban.
Oliver_C
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10100% kudos to the FAA for NOT waiting until there is an accident before taking action. – DJClayworth Mar 22 '11 at 15:30
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6How does this reconcile with international airlines such as Emirates Air allowing cellphones to be used during flights? Do they not care about safety? This would be surprising to me, given that they have one of the best safety records, and have never had a fatality in over a million flights. I'm not sure I'd want to fly in a plane that would drop out of the sky when someone turned on their phone, even if it was a million-to-one shot. For an airline to say that seems ridiculous. – Ezra Mar 22 '11 at 17:02
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@Ezra - There are a couple of airlines that allow cell phones to be used. They obviously must deem it safe. If they base this on empirical data only or if they actually have scientific evidence I don't know. – Oliver_C Mar 22 '11 at 17:44
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10Cell phones are prohibited so the fact that no accidents have happened while prohibited and thus low usage does not demonstrate that full use is risk free. – jjj Mar 22 '11 at 18:51
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4Something that results in a crash per day is not a low risk percentage. Clearly, because we don't have a crash per day, the industry/government players restrict and maintain things that remove risks that are less likely than .01%. Your percentage "proof" is a strawman argument. – Russell Steen Mar 22 '11 at 19:16
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11@Russell - my "percentage proof" wasn't intended as a proof, but as an attempt to explain why there is a ban. As long as there is even a small chance that cell phones can do harm, due to the large number of flights, it could still cause the loss of many lives. – Oliver_C Mar 22 '11 at 20:03
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5And yet, you say there are "10.000 flights per day". That statement on its own renders this whole point moot. Do you really think everyone turns off their phone on every flight? I'm sure every single one of those 10000 flights every day has at least a couple (probably a lot more) cellphones on them that are **not** turned off. If that isn't proof enough they do no harm, I don't know what is. – fretje Jul 12 '11 at 07:49
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1@Ezra most countries' aviation authorities will copy whatever the FAA does when it goes to regulations and adopt it as their own unless they have overriding reasons not to. – jwenting Oct 04 '11 at 08:42
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What about the vast differences in technology? That should prove it well enough. For example, the GPS receivers on the plane would be interrupted by what exactly that a cell phone or laptop could give off? They don't speak the same language, meaning, they aren't built off the same technology, and and where they are, they are using different frequencies, settings, etc. – Jun 10 '14 at 22:59
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@fredsbend: I just looked that up, and it looks like GPS operates around the 1600MHz band, and there do exist cellular networks on the 1700MHz band, though I don't have the knowledge to estimate what effect a few hundred phones blaring out across their spectrum would have on nearby bands. (And they would be, because at 20,000 feet you aren't going to connect to a cell tower, so their radios are going to be as high as they can go) – Phoshi Jun 11 '14 at 09:36
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@Phoshi Yes, several hundred phones on full search can make unexpected results; I am in favor of testing, but the point is that the FCC and FAA have worked together to make sure that any interference of any kind is a rarity, assuming no one is breaking the broadcast laws. – Jun 11 '14 at 15:47
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1This answer seems to be out of date http://www.foxbusiness.com/industries/2013/10/31/faa-relaxes-rules-allows-mobile-device-use-on-airplanes/ – Andy Mar 11 '15 at 22:03
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@Phoshi when taking off or landing, that is, when using electronic devices is forbidden, your plane is not 20.000 feet high... – Evargalo Feb 28 '18 at 12:40
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@fretje Actually, the average number of commercial flights per day is now around 100k. – Cloud May 23 '18 at 10:04
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Cell phones present a separate category, as they actively and intentionally transmit (i.e. generate E-M field), while the other appliances produce only a E-M noise, which is a lot weaker, see Small Aircraft RF Interference Path Loss:
For various reasons, many devices such as laptop computers are allowed during flights, while intentional transmitters such as wireless devices and phones are prohibited.
One particular issue with cell phones is that when they get far from the ground station (or lose connection to the ground station), they transmit a lot stronger signal to maintain the connection or to discover a station (the transmitted signal power varies in range 20 mW - 3 W, see also Mobile phone radiation). While one cell phone doing this would still most likely still be quite weak, having 400 cell phones transmitting at full intensity is something which could create an interference. This also explains why phones are not "confiscated" (like a knife would be) - a few of them left active does not matter, but having many of them could.
Besides of aircraft safety there are other concerns: active cells phones in the plane are bad for the phone operators, as the ground infrastructure is not designed for a situation like this. While the phone is quite far, it has a direct visual connection to many ground stations. See Mobile Phones and Aircraft
As the number of lines available in a particular cell is limited, the cells are sized according to the predicted number of simultaneous users. Inner-city cells are smaller than rural ones, based on the likelihood that there will be a greater demand for lines. Consequently, there are more cells per unit area in cities than elsewhere. It is also worth noting that the line-of-sight link from a mobile phone to a particular base station in a city is likely to be obstructed by buildings.
An aircraft could be carrying 500 cellphones. While passing directly over a city and thus unhindered by buildings, these phones could be in the line-of-sight of hundreds of base stations and could try to register with all of them. This would impose a temporary but extreme load on the network. The speed of the plane passing over the small inner-city cells would also result in an unusually rapid handover from cell to cell, possibly far in excess of the network's design limits.
It would be possible to provide an infrastructure on the plane to avoid the issues above, by having a dedicated station on the plane, which phones on board would connect to (this can be done with a weak signal, and with no need of any handover during the flight), and this station would then connect by one link to the ground network by some special means, e.g. using a satellite link. One paper attempting to design a scheme like this is ETSI White Paper No. 4, GSM operation onboard aircraft.
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2great answer. These are both the reasons I know. I also can add I have an engineer friend that went to school with me whom works for american airlines. If they want to allow an intentional radiator on the plane they have to get it certified safe. This requires a test flight. This is a very very large cost, and they have to do it per phone model, they consider it cost prohibitive and just ban phones as to avoid retesting constantly. – Kortuk Mar 24 '11 at 06:37
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the reasoning as to why the higher cell density in cities is not complete. Another overriding reason is the shorter range due to signal deterioration in and around buildings. That's also why towers are often placed such as to have a clear line of sight down roads, rather than in blind corners. – jwenting Oct 04 '11 at 08:45
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The FAA regulation is based on a study from the RTCA which does indicate that cell phones can interfere with critical systems.
Clearly they do not interfere every time, and not every interference would result in a crash, and proof after the fact would be difficult. So the fact that no crashes have been blamed on this is not, by itself, proof that they pose no risk.
As to why all devices might be banned, airlines tend to err on the side of less lawsuits and less violations. The regulatory policy is clear that Airlines (in the US) are responsible for the effects of electronic devices operated on their planes, so they are going to be very hesitant to allow usage -- especially since research by the RTCA shows that some devices do interfere.
Russell Steen
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4The airlines don't have a choice anyways on the cell phones. The FCC says "thou shalt not use cellphones in flight". Other electronic equipment is restricted by FAA requirements (which varies based on IFR or VFR flight, and sometimes by what the PIC chooses to allow). – Brian Knoblauch Mar 24 '11 at 20:07
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another reason for a blanket ban is the impossibility of testing and verifying each and every piece of electronics a potential passenger might have in his posession, let alone training flight attendants to recognise and differentiate between all of them (often placed in covers, bags, skins) and remember which are or are not allowed. And situations like "yes sir, your eReader has to be turned off because it has a WiFi transmitter, the person next to you has a different model without such a transmitter so it is ok" isn't going to go down well with many passengers either. – jwenting Oct 04 '11 at 08:48
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It appears it is based on reasonable data. I have no knowledge about any FAA research, but (not so recently) the Mythbusters tackled the myth that it is forbidden to use cellphones to force you to use the on-board phones.
They had to build their own mock-up cockpit and throw a whole lot of interference-causing stuff at it, which sort of worked. However it supposedly only worked because the wires in their mock-up weren't properly shielded. This would be supported by their failure to cause any sort of interference in a corporate jet (a Hawker 800XP).
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It's not just a matter of poor shielding. You _can't_ shield the antennas of the radionavigation equipment. If some random poorly-manufactured (or damaged) device just happens to start emitting noise on the frequency used by the localizer or glideslope, they can throw off the ILS readings, which is extremely unhelpful when you're trying to land in low visibility conditions. ILS is still a surprisingly-simplistic system that isn't very difficult to fool. It's literally just a couple of directional AM signals and a measurement of their interference pattern (designed in the 1930s or 40s, IIRC.) – reirab Jan 09 '15 at 17:39
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As to no reported incidents, there is at least one. It was due to a passenger's refusal to turn off a boom box which interfered with the aircraft's navigational equipment. See, US v. Hicks, 980 F. 2d 963 (5th Cir.1992) retrieved from: https://scholar.google.co.th/scholar_case?case=6625292697406630772&q=boombox+interference+with+flight+crew&hl=en&as_sdt=2003
Michael Kane
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[Welcome to Skeptics!](http://meta.skeptics.stackexchange.com/questions/1505/welcome-to-new-users) This is poor evidence. It consists of a pilot committing a "post hoc ergo propter hoc" fallacy. It doesn't show that the boom box actually interfered with the aircraft's navigational equipment. – Oddthinking Aug 23 '18 at 15:14
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It was not merely a question of the pilot's personal views. Federal officers made an arrest. Evidence was presented to a grand jury, which returned an indictment. A trial was had before a judge and jury. And Mr. Hicks was convicted based on the evidence. It may be "poor evidence" but it was sufficient enough to deprive him of his liberty for a term of years. – Michael Kane Sep 11 '18 at 12:21