Travel Technology - Aircraft instrument interference from cellphone

I know the topic of prohibition of electronics during take off and landing comes up fairly often, but here's a case where it looks like it actually makes sense (http://blog.aopa.org/leadingedge/?p=2037).


A CRJ flying at 9,000’ received an EFIS COMP MON caution message:

“Flight Manual directs pilots to slew compass to reliable side. It was apparent neither side was correct with the Captain’s, Mag Compass, and First Officer’s headings all different. We were cleared direct to a fix. Multiple attempts were made to match the headings with only temporary results. The Captain elected to hand fly while the headings mismatched. While the FMS was taking us in a direct line, with the wind shift while hand flying the aircraft ended up 4 miles south of the original ‘direct to’ course. ATC called and asked if we were going direct, I told them we are having heading problems and asked how our heading looked. He told us 10 right and direct when able. On this trip we flew this same aircraft for 9 legs and did not have this problem on any other flight. In the past I have had similar events with speculation that cellphones left on may contribute to the heading problems.

The first Officer made a PA announcement asking everyone to check their cellphones and the flight attendant walked through the cabin. Sure enough, in Row 9 was a phone in standby mode—not airplane mode. The passenger said he didn’t know how to program that so the flight attendant showed him and as soon as the phone was secured, all the avionics worked perfectly.”


So admittedly cellphones are designed to transmit and many electronics aren't (although kindles/nooks/etc usually at least have Wifi or the like), but I think we can all get the appropriate message from this ASRS report: never fly on CRJs. :D

Just another anecdotal claim about cell phones interfering with the airplane, but with no proof. Color me shocked. :rolleyes:

Dunno. A report by an airline pilot or copilot of interference that ceases when the phone is secured seems like proof of the phone being the source, although you are right that it is anecdotal and the plural of anecdote is not data...

Just think about it. If cell phones could truly cause interference with the flight systems terrorists would just bring electronic devices on board that transmit waves so that they could interfere with the navigational systems. It would be so easy to do. It simply doesn't make sense that they would actually interfere.

As someone who's analyzed numerous scientific studies, I can say with certainty that you cannot make any conclusion whatsoever based on this situation. Even without knowing the technical aspects of navigational equipment and waves, there are so many other confounding variables that there's no way to tell what the cause of these issues was. One possibility is that they flew through a specific area that for some reason had interference of some kind. I'd like to see what happens when that same person travels on another flight with their phone in standby (or what would have happened if he put his phone back on standby).

Dunno. A report by an airline pilot or copilot of interference that ceases when the phone is secured seems like proof of the phone being the source, although you are right that it is anecdotal and the plural of anecdote is not data...

Correlation is not the same thing as causation

I think the real point is this:

Put your cellphone in airplane mode when you get on a plane.

If you don't know how to put your phone into airplane mode, shut the thing off.

I think the real point is this:

Put your cellphone in airplane mode when you get on a plane.

If you don't know how to put your phone into airplane mode, shut the thing off.

Actually, the real point is that in over 300 million commercial flights in the last 30 years there is not one single proven case of interference by a consumer electronic device. Turn off your device if you want to save your battery, but that is all you will be doing, nothing more.

Mythbusters tried to get this to work and could not ,
even with much more wattage that a cell phone would ever put out ,

and i still turn mine off ,

soarer

Just think about it. If cell phones could truly cause interference with the flight systems terrorists would just bring electronic devices on board that transmit waves so that they could interfere with the navigational systems. It would be so easy to do. It simply doesn't make sense that they would actually interfere.


Or, more likely, if cell phones did truly cause interference we would have heard a lot more about it than a handful of apocryphal anecdotes, given the millions upon millions of flights and likely thousands or millions of cell phones left on by mistake over the years. And the TSA would ban cell phones along with explosives.

Or, more likely, if cell phones did truly cause interference we would have heard a lot more about it than a handful of apocryphal anecdotes, given the millions upon millions of flights and likely thousands or millions of cell phones left on by mistake over the years. And the TSA would ban cell phones along with explosives.

The International Air Transport Association (IATA) released passenger and freight traffic forecasts projecting that in 2011 the air transport industry will handle 2.75 billion passengers (620 million more passengers than in 2006)
http://www.iata.org/pressroom/pr/pages/2007-24-10-01.aspx

The US alone has over 9 million flights per year http://www.transtats.bts.gov/

Over 2 billion pax per year. Estimate that 0.1% leave their cell phones on (probably a low estimate based on my observations). That's over 2 million per year. Pure coincidence easily accounts for a few instances in which it appears cell phones caused issues.

FWIW; the full report with all incidents is here:

http://asrs.arc.nasa.gov/docs/rpsts/ped.pdf

Any transmitting device can bleed over if working improperly, much like the CB did in days of old when they go into the neighbors TV.

Secondary harmonic-es can and do put out a signal, most of the time it is not harmful, but their has been time it has need heard on TVs.. Ham Raido Cop Cars etc.

We use to have crystal radios, no tubes just picking up the transmission of radio stations.

Circuits are much better shielded and designed today...

Not too hard to find a transmitter so turn them off...

FWIW; the full report with all incidents is here:

http://asrs.arc.nasa.gov/docs/rpsts/ped.pdf

Thanks, I went looking for the actual ASRS report before posting and didn't succeed in finding it.

Many planes now have wifi which means a good amount of people on the flight are on their laptops or phones in "non-airplane" mode. Is there a reason that the FAA believes that's safe, but on planes that don't have that ability it's not safe? Do the planes that are equipped with that have different navigational equipment or something like that?

Aircraft go through all sorts of RF interference testing before they are airworthy. The reason phones must be turned off is because it's virtually impossible for the FAA (or other governing body) to test every single device to make sure it doesn't cause issues.

Since some carriers now allow mobile phones and wifi in flight, I think it's pretty obvious they aren't a risk.

The main reason to have PED's turned off on takeoff/landing is to keep pax focused and ready in case of emergency.

I'd be willing to bet that in the OP's scenario, whatever the pax was using wasn't a mobile phone. They could have easily brought a VHF transmitter on board.

FWIW; the full report with all incidents is here:

http://asrs.arc.nasa.gov/docs/rpsts/ped.pdf

The majority of those issues are pax behavior issues. Actually, very few, perhaps none have anything to do with phones causing issues.

That being said, I found this one most interesting:

Synopsis
A passenger's Kindle Reader was crushed when a First Class Sleeper seat was
retracted causing a fire and smoke. A Flight Attendant put the fire out while the
flight crew accomplished the Smoke and Fire Checklist, including declaring an
emergency.

The main reason to have PED's turned off on takeoff/landing is to keep pax focused and ready in case of emergency.
this line of reasoning also seems weak, given that in the old days we'd just be buried in a book not a device - and nobody ever got told to put the books away.

Aircraft go through all sorts of RF interference testing before they are airworthy. .

Really, even those 30 year old AA MD80's? Problem is there are plenty of airframes flying that weren't tested against today's potential RF environment.

Really, even those 30 year old AA MD80's? Problem is there are plenty of airframes flying that weren't tested against today's potential RF environment.

Yet they have made many millions of flights without a SINGLE PROVEN CASE OF INTERFERENCE. Yeah, boy, that sure sounds like something to get all worried about.

:rolleyes:

The wifi installed in an aircraft, just like sat phones back when they were popular, are part of the aircraft's equiptment. They are tested & certified by FAA (or other competent authority), just like the nav system, landing gear and fuel tanks. In fact, everything from tray tables to potable water spigots is tested and part of the aircraft.

Not so for cell phones and other devices.

It's all about managing risk. And, the way to manage risk in the air is to make sure that if it isn't tested, it's not being used during critical phases of the flight.

If any of you have been on a call with a speaker phone and someone has a Blackberry in the room, you have heard the little beep when the Bberry polls. That's merely annoying. But, if that beep blocks the Captain's communications with ATC while the aircraft is being vectored around traffic, it can be fatal.

There's a reason that commercial aviation has never been safer and it's a matter of paying attention to detail. That has paid off.

So why do it when the cabin door closes? Because people don't listen and need to be reminded. There's a hard line of when the phones go off. Can guarantee you that if carriers allowed cell phones up to 30 secs. before takeoff, there would be some fool who would wait until 10 secs. or maybe figure it's OK to talk until wheels are actually up and so on.

Yet they have made many millions of flights without a SINGLE PROVEN CASE OF INTERFERENCE. Yeah, boy, that sure sounds like something to get all worried about.

:rolleyes:

While I think that the electronic ban is over cautious and essentially unenforceable, the argument quoted is not adequate. The question is "how many flights have been conducted with all of the passenger electronics powered up?" as that would be closer to reality if the regulations were relaxed.

Personally, I think there is a lot of silliness. Bureaucratic behavior on the part of the regulators. Childish behavior on the part of passengers addicted to their electronic binkies. (me too. I wish I could have my noise cancelling headphones powered up when the engines are powered up. I think only WN is enlightened on this among the major carriers).

Actually, the real point is that in over 300 million commercial flights in the last 30 years there is not one single proven case of interference by a consumer electronic device. Turn off your device if you want to save your battery, but that is all you will be doing, nothing more.

Aircraft go through all sorts of RF interference testing before they are airworthy. The reason phones must be turned off is because it's virtually impossible for the FAA (or other governing body) to test every single device to make sure it doesn't cause issues.
Precisely. Certification is not given on the basis of "this is not a risk as it has never happened" There has to be reproducible scientific data that can establish that it does not and cannot, interfere with other systems.

It's not enough to look at power levels and harmonics, as some have suggested in other threads on this topic. You also have to look at beats and multi-path propagation . A proper calculation is a complicated one, I am sure it can be done, and probably has been for a generic aircraft, but that would not be sufficient to certify every aircraft.
Multitude of PEDs operating at various power levels scattered throughout the aircraft makes it increasingly difficult to "certify" that there would be no EMI related accident. It wouldn;t take much for a lawyer to present something like the OP and bankrupt an airline in case of an accident.
With increasing number of electronic devices, it's an EM jungle out there.
EMI (electromagnetic interference) is done for military platforms, such as a ship. There are times when complete EM silence is enforced. The combined effect of a random set of a large number of electronic devices is not predictable.
There is empirical evidence that no aircraft has ever been involved in an accident due to a cell phone.-True. But that's not the point. The point is whether one can or/and wants to spend the time and money to prove scientifically,
More over, empirical evidence cannot be the guide here.
Existence of neutrino was first proposed around 1930, to explain the spectrum of decay products in beta decay. The only way the experimental results could be consistent with laws of physics (conservation of energy, momentum and spin) was to incorporate another brand new particle into the equations. For more than a quarter of century, no experiment could detect a neutrino. Using the empirical argument, one could have said "Neutrino is a fantasy, or even a conspiracy, created by Pauli. Neutrinos have never been observed. So they don;t exist." There are still particles that have not been detected. It simply means that they have not been detected, but it does not prove that they don't exist. :D

It very well maybe that PEDs would not interfere. But that's an opinion, not a scientifically drawn conclusion.
EMI deniers in the same camp as climate change deniers simply use their hunch, not scientific principles to support their claim.

Also, it's necessary did not have their PEDs in their hands if an emergency arises. Why spend limited resources one something so silly as the ability to use any PED inflight?

I can't imagine being on a plane with 300-400 people talking on their mobile phones. It's best of the ban stays.

There is empirical evidence that no aircraft has ever been involved in an accident due to a cell phone.-True. But that's not the point. The point is whether one can or/and wants to spend the time and money to prove scientifically,
More over, empirical evidence cannot be the guide here.
Empirical evidence is essential to the scientific method. Science is basically forming a hypothesis and testing it empirically. You might want to read http://en.wikipedia.org/wiki/Scientific_method

Your post conflates certification, legal standards and the scientific method. They are not the same thing.

We are trying to demonstrate whether or not something exists. If we find one example of something, then we've proved it exists. Not finding one after running adequate experiments is evidence that something does not exist, but it is seldom possible to prove something doesn't exist if it might exist in theory. All you can say is we have a degree of confidence it doesn't exist. How high our confidence is depends on theory and the quality and quantity of empirical evidence.

The FAA certification process is a testing method. The informal testing by billions of passengers is another testing method. Neither is absolute proof, but the large number of trials is strong evidence.

Cellphones on planes is a profoundly dumb idea for those who'd like some quiet in the sky, but that's another question.

Empirical evidence is essential to the scientific method. Science is basically forming a hypothesis and testing it empirically. You might want to read http://en.wikipedia.org/wiki/Scientific_method
No I certainly shan't read that silly link.
Is Wikipedia the best you can do? :p
If we are going to discuss this, please be respectful.
Wikipedia and science are what "People's Magazine" is to "The TImes"
Empirical evidence is essential but not sufficient. @:-) I have never said anywhere that empirical evidence should ignored.
How do I argue with someone who reads what I have not written and does not understand the difference between essential and sufficient--both important for conducting a discussion-- but cites Wikipedia link on scientific method to me. :p
Nevertheless, I shall try.
Your post conflates certification, legal standards and the scientific method. They are not the same thing.
Conflate is a nice word. It would be nicer if the person arguing about EMI would not be so condescending and complacent.
Please try and understand instead of insulting me. We are not discussing what a scientific method is, nor do I need instruction in it.
I suspect you know little about basic aspects of the problem, which has two parts.

Calculating the strength of an electromagnetic field, given a distribution of EM sources--the total field.
What is that minimum level of field strength which the total field must not exceed in order not to cause EMI under any circumstances.


There is really not much to be to be gained in terms of fundamental physics by investigating how much interference a collection of stray and an indefinite number of randomly distributed sources of electromagnetic signals can cause with aircraft systems. It is, however, of practical significance, especially to some, here, who must, have their gadgets on at will. The answer is not as trivial as citing a Wikipedia link. I assure you my friend, that there is nothing Wikipedia can do in terms of shedding light on this issue. This problem is not a trivial one and requires a considerable level of effort, by experts in electromagnetic propagation in conducting and non-conducting media.
Strictly speaking, the problem is different for every aircraft and for every flight. But simplifications and assumptions can be made.
Someone must pay to conduct that investigation
For some passengers, it's not even a matter of practical significance.
What I have stated above is the gist of the problem.
The rest of what you wrote s garbage as far as physics of the problem is concerned. BY garbage, I don't mean any disrespect, but that it's not relevant and should be neglected and ignored if we are to get closer to the solution.
We are trying to demonstrate whether or not something exists. If we find one example of something, then we've proved it exists. Not finding one after running adequate experiments is evidence that something does not exist, but it is seldom possible to prove something doesn't exist if it might exist in theory. All you can say is we have a degree of confidence it doesn't exist. How high our confidence is depends on theory and the quality and quantity of empirical evidence.
My dear sir, on the one hand you cite a Wikipedia link to "scientific method" and on the other, post the above.
Let's take existence. What is it whose existence you are talking about?
Electromagnetic waves do exist. Electromagnetic waves do travel, with the speed of light. And the Electromagnetic field over the distance between passengers and the instruments is not insignificant. Everything I am talking about exists. Are you talking about an aircraft accident caused by a cell phone? Existence has nothing to do with it.
What experiments are you talking about? All we have is anecdotes, many many anecdotes. That's not science my friend. Tell me how you are going to quantify the probability in this case when you have absolutely no data about anything?

The FAA certification process is a testing method. The informal testing by billions of passengers is another testing method. Neither is absolute proof, but the large number of trials is strong evidence.
Cellphones on planes is a profoundly dumb idea for those who'd like some quiet in the sky, but that's another question.
What you call informal testing is NOT testing at all. It's happenstance.
Now FAA rules are based on what was known and the state of technology that existed when the rules were made. I am not familiar with FAA standards, but am familiar with military standards for EMI in several countries. When you design something, you do calculations, as well as tests and present your data to those charged with enforcing the standards. Then there are field trials. Unless you have done a all of the above, you cannot make a claim. Mr. Boeing certainly isn't going to say, "Look Mr FAA. Millions of passengers of passengers like Mr Yaatri and Mr. richarddd, covering a wide range from brilliant to ignorant (just kidding here) travel every day on Boeing aircraft, some with their cellphones and other gadgets on, in spite of your regulations, but no aircraft has crashed yet. So please certify my aircraft to be safe with PEDs. I doubt that Mr Airbus or any airlines would do that either.

That is the real situation. Neither the airlines, nor the aircraft manufacturer have any incentive to seek the kind of certification people want.
As the rules stand, Airlines are responsible for ensuring compliance with all FAA regulations, including those for safety and EMI/EMC. Unless someone comes and convinces the body that establishes Standards (I happen to be on one standards committee , not for EMI/EMC though), nothing is going to change. Professional, industrial and scientific organisations such as APS, IEEE, ASME and even manufacturers have standards committees that develop technical recommendations for products and standards, that are reviewed by govet agencies and turned into Standards. FAA is not know it all. FAA is pretty dumb actually. Standards are the result of collective effort of scientists, engineers, from industry and academic institutions, along with skilled workers and the Govt agencies. They all have to agree.
I hope this explains. Then we have the congress, which can do anything--even legislate laws of physics. :D

Yet they have made many millions of flights without a SINGLE PROVEN CASE OF INTERFERENCE. Yeah, boy, that sure sounds like something to get all worried about.

:rolleyes:

Mr. planemechanic, I respect your professional knowledge, but am fraid, I have to disagree with this logic of yours. .

With all due respect Yaatri (I can't even begin to comprehend the majority of what you've written here :)), while Wikipedia isn't exactly a scientific source, I think it's perfectly appropriate to cite a Wikipedia article for something like describing the scientific method. It would be inappropriate to cite a Wikipedia article that describes EMI perhaps (I don't even know what that means) but the scientific method is just about how to conduct investigations, not anything specific about any particular investigation. I don't think you can use the fact that richarddd linked a Wikipedia article to "ad hominem him".

No I certainly shan't read that silly link.
Is Wikipedia the best you can do? :p
Wikipedia clearly explains the scientific method. If you have a problem with its explanation of the scientific method requiring formulating hypotheses and then testing them with experiments, there's no reason to continue.

Yet they have made many millions of flights without a SINGLE PROVEN CASE OF INTERFERENCE. Yeah, boy, that sure sounds like something to get all worried about.


...and before AA191 crashed, there wasn't a single proven case of a DC-10's engine ripping off at takeoff...

Admittedly the consequences of these failures aren't comparable, but in the presence of anecdotal evidence suggesting a correlation between EM/RF interference and the malfunctioning of avionics, I'm willing to err on the side of caution.

I'm a private pilot, and I've experienced cell phone interference in the cockpit. My flight instructor would often text or even talk on her cell phone; I didn't have any problem with this practice since everything was day VFR and there's not much that's going to fail in a Cessna 150. Still, it's pretty easy to correlate an outgoing cell phone call with the "dada-da-dadada" audible interference over the intercom. I'm sure everyone here has experienced some form of RF interference over intercoms, speakers, or other unshielded consumer electronics.

All I'm saying is that cell phones transmit electromagnetic radiation at varying intensities and frequencies. Aircraft rely on any number of electronic systems with any number of wiring configurations. With an infinite number of cell phones and an infinite number of planes, at some point you're going to find a bad combination of systems which will result in a malfunction. Yes, the malfunction will likely be in a navigational or communications system (the engines won't fall off or the plane plummet), but I certainly don't want to be at 100' AGL shooting a CAT III ILS while a plane load of passengers is texting.

Out of an abundance of caution I would prefer to reduce the sources of potential electronic interference, especially at critical phases of flight where that interference could cause harm.

Wikipedia clearly explains the scientific method. If you have a problem with its explanation of the scientific method requiring formulating hypotheses and then testing them with experiments, there's no reason to continue.

No, I don;t have a problem with explanation of scientific method, as I am a scientist. I do have a problem with being directed to an article on scientific method while completely disregarding evidence and calling anecdotes scientific experiment.

With all due respect Yaatri (I can't even begin to comprehend the majority of what you've written here :)), while Wikipedia isn't exactly a scientific source, I think it's perfectly appropriate to cite a Wikipedia article for something like describing the scientific method. It would be inappropriate to cite a Wikipedia article that describes EMI perhaps (I don't even know what that means) but the scientific method is just about how to conduct investigations, not anything specific about any particular investigation. I don't think you can use the fact that richarddd linked a Wikipedia article to "ad hominem him".

Reference to a wikipedia article on scientific method by someone who is not the least bit scientific in their approach is silly.

I am afraid, it's difficult to discuss a very technical issue in a general forum as this one. However, I tried. I am quite good at explaining technical material to lay people, provided there is a sincere willingness and a desire to understand. I have taught courses in electromagnetic propagation, which students have greatly appreciated. It was easier to teach than explain here because students asked relevant questions, instead of directing me to read what scientific method is.
My ability to explain highly technical issues to lay people who would be reading my reports has been noted by various customers of my employer.
EMI is electromagnetic interference
EMC is Electromagnetic compliance.
Please ignore all references to the Wikipedia article and read my post again. I will be happy to explain again if you have specific questions.
I have not strayed from scientific method. hence asking me to read a Wikipedia article about scientific method is a completely unscientific distraction.
Perhaps I can explain better if you tell me why you think PED's can never cause interference in words other than, "it has never happened before so it can't happen again".

Just to add fuel to the fire, what about Crossair Flight 498?

I am an electrical engineer with a degree and work experience in electromagnetic radiation.

First Point: To those who say that planes take off every day with electronic devices turned on without mishap, let me give a simple non-technical analogy. You cross a pond one million times in a row boat. You conclude that the rowboat cannot sink because it hasn't so far. So you feel safe in putting 100 people in the rowboat and head across. I doubt if any plane has taken off with every electronic device turned on. There is no precedent.

Second Point: I suspect that the probability of a lithium battery fire (which increases with the device being on) is greater than the probability of electronic interference. This is only a suspicion since I have not done the study to investigate it.

Third Point: Many electronic devices are not truly off unless the battery is taken out of it. Anything with a non-mechanical on/off switch will have at least one circuit powered. Keep in mind that EMI does not require transmitting capability by the device.

Mr. planemechanic, I respect your professional knowledge, but am fraid, I have to disagree with this logic of yours. .

You disagree that there have been 300 million commercial airline flights in the past 30 years with not one documents case of a crash, diversion, injury or death that was confirmed to have been caused by a PED?

This rule, as with all rules that appear to defy reality and conventional wisdom, will be and is being ignored by the traveling public, all to no ill effect. No one should be surprised.

Just to add fuel to the fire, what about Crossair Flight 498?

Just another speculative case with zero evidence of any actual impact on the aircraft or crew, despite a detailed analysis of the flight, the flight recorders, and the crew.

I thought some agency, either US or EU, was studying allowing the use of cell phones.

It's one thing to text or surf on a phone but voice calls would probably antagonize other passengers.

How would they allow people to use all functions of the phone but voice calls?

'Mobile phone brings down Slovenian airplane' -circa 2001

http://www.theregister.co.uk/2001/01/11/mobile_phone_brings_down_slovenian/

Yaatri, I didn't mean to imply that you didn't explain any of this appropriately. To be honest, I'm pretty good at learning things that I'm interested in and I'm sure that if I was very interested in this topic you would have no trouble explaining it to me and I would be able to comprehend some of it (obviously there's no way I could become well-versed in something like this by just spending 30 minutes reading, even from the best teacher). I added that parenthetical mostly to just state that I don't know about the engineering aspect of this discussion.

I am also not saying that you strayed at all from the scientific method. Further, I didn't mean to imply that you aren't well versed in the scientific method, and as someone who's relatively well versed in the scientific method (biology, not engineering-but the idea is still the same), I understand the point you're making that richardd's implication of you not knowing the scientific method was unfounded. I personally don't see why he believed you didn't understand the scientific method.

The only thing I really meant to state was that I think it's perfectly fine to link a Wikipedia article to describe the scientific method.

You disagree that there have been 300 million commercial airline flights in the past 30 years with not one documents case of a crash, diversion, injury or death that was confirmed to have been caused by a PED?
LOL no. I disagree with your conclusion not the observation, which I have boled.

This rule, as with all rules that appear to defy reality and conventional wisdom, will be and is being ignored by the traveling public, all to no ill effect. No one should be surprised.

The reality is simply that it has not happened. And that it cannot be said that a PED cannot, under any circumstances, cause EMI, becuase it does, Its significance is often inconsequential. That is the reality.

And what about private jets? Think of how many corporate execs and wealthy individuals are flying around every day. They darn sure aren't turning off their cell phones yet this hasn't caused any crashes AFAIK.

I thought some agency, either US or EU, was studying allowing the use of cell phones.

It's one thing to text or surf on a phone but voice calls would probably antagonize other passengers.

How would they allow people to use all functions of the phone but voice calls?

The base station hardware the planes will carry will simply not provide voice services.

Phones can connect to towers on the ground.

Phones can connect to towers on the ground.

Below, 10,000 feet? I've done it, and uploaded pictures to Facebook.

At 30,000 feet? Not usefully. Towers point down, there's too many to be seen at altitude for phones to make a useful decision about which one to communicate with, and they're far enough away that a cell phone in a big metal can isn't going to reach the base station.

I turn my phone off most of the time , sometimes I forget or fall asleep and forget ,

But why would you want to leave it on while in flight ?
you are not going to get calls or texts at 30,000 ft !

Soarer