What’s Going On Between Airlines And 5G?

Several international airlines paused Boeing 777 routes to the U.S. over questions of whether the FAA would allow them to land in the U.S. under normal conditions or whether flights would be required to divert over technical concerns. U.S. airlines filed diversion plans for some flights in case their planes weren’t allowed to land at major U.S. airports where 5G was going to get rolled out. And the 5G service rollout was partially delayed again.

And it’s all either a trumped up non-issue, or an aviation apocalypse, depending on whom you ask. The worry is that C-band 5G at the power and frequency that will be used in the U.S. could send confusing signals to radio altimeters in aircraft, leading to confusion over the altitude at which the plane is flying, and problems for other systems in some aircraft like Boeing 777s as well. What’s going on here?

  • 5G should be fine. 5G rollout has been figured out in Europe without a conflict with aircraft altimeters, and there’s even a bigger frequency buffer in the U.S. So the band gap is enough that altimeters shouldn’t have a problem, but there may be some limited circumstances where they do anyway because of the specific different frequencies being used here. The altimeters needed to be updated, and weren’t. We don’t actually know this will be an issue, there’s some very limited data suggesting it could be. And aviation doesn’t take even small risks.

  • There’s a potential problem with the altimeters which don’t seem to be masking out of band signals, since there wasn’t anything which would have been a conflict with the signal range they used 40 years ago when their standards were put in place. So there was no reason to add cost and complexity. But this should all have been dealt with years ago and wasn’t.

  • Everyone closed their eyes and played chicken. 5G rollout has been known for years, with published specifications, and at the last minute there’s a game of chicken. There’s plenty of data suggesting this would be fine, and the government agency in charge (FCC) signed off, which telecomm agencies relied on in spending $80.9 billion in the government auction which gives them the right to roll out 5G using specs determined by the feds.

  • Turf war between regulatory agencies, with the FAA raising its concerns at the last minute. They’ll say that there were issues noted earlier but that’s barely true in the most technical of senses. But the FAA has a hammer, which is the ability to regulate airlines in an extreme manner. And no one wants to see major disruption to aviation, and no one wants to do anything that will lead them to be blamed for an accident (even if it turns out to have nothing to do with 5G). And the disruption of FAA restrictions is massive. As American Airlines Chairman Doug Parker told employees earlier this month,

    There were two days in the last couple of weeks of December..if we could only fly Cat 1 Dallas and DFW wouldn’t have opened until 10 a.m.

    If DFW doesn’t open until 10 a.m. that’s 400 cancellations. And that’s if we knew about it the night before. That’s if we don’t start launching airplanes and then divert.. we didn’t cancel 400 flights on the mainline through all of this mess. Those are two days that were perfectly fine operations.

    …The altimeter is used for other parts of the airplane…It’s tied to the heads up display. Boeing has it tied to..help with tail strikes on the 777-300s, all sorts of things that if you’re concerned about the use of the altimater we’re not going to be flying 777-300s into any affected airport.

    Meanwhile the FCC knows there’s been plenty of notice, their studies suggest this should all be fine, and lacks sympathy for engineers who didn’t address concerns they may have had with mission-critical systems for years.

So what happens next? Everyone finds a temporary fix to a limited set of planes and airports and defers major costs.

There needs to be a retrofit of existing altimeters, perhaps in some case replacement. We don’t really know whether there’s risk of displaying wrong altitude or other issues with existing altimeters since the FAA hasn’t done much to study the issue over the past several years. Now they want time.

5G is actually very valuable to the public, and the retrofit costs are much smaller than the benefit to the service. This is indisputable. But there’s also jockeying not just for time but over ‘who pays’. And a crisis facilitates potentially getting the government to pay, out of a portion of that $80 billion from the spectrum auction perhaps.

This conclusion from reader Steve seems right to me, who notes that we probably should agree to pay for altimeter upgrades out of auction proceeds to ratchet down the rhetoric.

Nobody is going to want to be the one to decide the risks with the current altimeters are small and end up with a crash, even if it turns out later to have nothing to do with this issue and since shutting down 5G is a shifted cost (ie it doesn’t fall on the airlines) they are going to scream for as much as they can get arguing the inconvienence of not having faster cellphones is outweighted by not killing people (really the remote chance of killing people).

The right answer is a fast track program for outfitting those altimeters that can with an inline filter and replacing those that can’t. That would be a boon to any companies that have a certified solution since they’d just have to scale up production but even that will take months so it will come down to how much of the 5G coverage the airlines/Boeing vs the cell companies can agree is enough.

Given the political power of each side that could turn out to be a very interesting fight. What I’m sure will be lost is any sort of rational decision making and it sidesteps the real problem which is why given it’s been known for years that these frequencies were set to be utilized these tests were only ran just over a year ago and the issue is only coming to a head now.

About Gary Leff

Gary Leff is one of the foremost experts in the field of miles, points, and frequent business travel - a topic he has covered since 2002. Co-founder of frequent flyer community InsideFlyer.com, emcee of the Freddie Awards, and named one of the "World's Top Travel Experts" by Conde' Nast Traveler (2010-Present) Gary has been a guest on most major news media, profiled in several top print publications, and published broadly on the topic of consumer loyalty. More About Gary »

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  1. It’s really pretty simple.

    5G in the US is not being deployed in the same way as in other countries. Period. Comparisons to what other countries have done is meaningless. FULL STOP.

    No one wants to be responsible for hundreds of cancelled flights let alone a possible landing failure that could result in the loss of life.

    The FAA and airline industry have raised concerns for years. The FCC blew it all off at the behest of making billions on 5G frequency auctions.

    Boeing and the FAA have raised concerns and have put regulations in place that prohibit some normal operations.

    Airlines don’t make rules; they are required to follow them.

    When the FCC and FAA get it figured out and airframe manufacturers remove their advisories and reinstate approvals for normal operations, then all will be fine.

    And until then, the next major weather event in NYC, Dallas, Chicago or Miami will likely result in the cancellation of scores of longhaul international flights – even after American’s CEO said it was all no big deal – and then signed a letter expressing grave concerns.

  2. The incompetence of the United States government continues to hit new lows. The FCC determined years ago that this wasn’t a problem, it hasn’t been a real world problem anywhere 5G has been deployed, including in places like China and Europe where 5G is working besides normal aviation operations, and yet Americans have neither 5G nor normal aviation operations because the Biden Administration fails to follow the science – an emerging theme of this Administration – and instead panic over phantoms. So China and Europe have 5G, and the US is using an obsolete wireless standard because . . . ?

    By the way, I love all the media coverage of Emirates decision to cancel their flights yesterday, as if the scientific consensus in the UAE should be terribly convincing after the extensive analysis in the USA, Europe, China, etc. What a joke.

  3. One of the problems that make comparisons to Europe and Asia useless is that some of the frequency ranges used in North America are located on bands that are adjacent to navigational data transmissions. Not the case overseas. But, this has been coming for years and the day of implementation is not the time for a tantrum. That should have happened years ago.

  4. @Mak.
    “Yet a simpler and more serious lesson might also have emerged. This dust-up spilled over from the previous administration, which allowed crucial positions, including for some time the chief of the NTIA, to remain empty. (This month, a new chief was finally confirmed.) More generally, President Donald Trump’s White House displayed disregard for the intricacies of the inner, quieter workings of the executive branch. These intricacies, it turns out, matter: to keep the lights on, to keep the planes flying and to keep our phones up to modern-day snuff.”

    This from the WaPo. See, there is plenty of blame to go around. Which is why this is a mess. Everyone is pointing fingers. Just find a solution and move on.

  5. So what I don’t get is why wasn’t this addressed during the Pandemic when flights were grounded, the airlines were getting $79b in aid and we all knew this was going to happen. I don’t get it. This was an investment that could have been made then to avoid all of this. This is a breakdown on all sides that should have been addressed years ago.

  6. I’m an AT&T user with 5GE service. I couldn’t get ANY cellular data coverage this morning at Detroit’s airport.

  7. The FCC did extensive field testing and found 5G did not interfere with the safe operation of radar altimeters. The FCC has a mountain of field data. Let’s see if that data is “externally” valid. During clear weather conditions — a non-fatal scenario — monitor the performance of radar altimeters for 5G interference. Then move into progressively worse weather conditions.

    Everyone freaked out over phones and tablets. Now look where we are.

    Experience and observation will tell us.

  8. Can we stop with blaming whatever administration Please?
    This started 20 years ago and has crossed many administrations of both parties. It looks like FAA vs FCC vs bureaucratic inertia.
    Solutions please not attacks…..

  9. Airlines are trying to make money out of this scare tactic. Similar to the no cell phone issue or fear of laptops on airplanes. People are scared of stuff. We see that with vaccines, we see it with technology while they believe all kinds of even dumber conspiracies or willingly take OTC medicines that are largely useless if not harmful.

  10. @Stuart this is total nonsense. FCC had an extended reasoned decision making process culminating in 100s of pages of explicit findings. There is no serious argument that FCCs decision was in any way political or tainted by Trump and nobody ever posed any serious challenge previously – they could not. There is no scientific controversy about the spectrum, the auction (for frequencies already in use) or the process that accomplished them. The only possible controversy is speculation that some navigation systems are not well designed and interfere or are interfering with spectrum belonging to others – and that’s their problem, not anybody else’s. If incompetents ignored that problem and hoped this day would never arrive, they should pay the price and ground their planes.

  11. @Gary

    :……and there’s even a bigger frequency buffer in the U.S. ”

    Could you provide a source for this claim? Reuters reports that the EU 5g operates in the 3.4-3.8 GHz range, and that the US 5g operates in the 3.7-3.98 GHz range. Altimeters from all operate in the 4.2-4.4 GHz, yielding a 180 MHz narrower frequency buffer in the USA than in the EU. There are a host of other differences between other countries that have implemented 5g without problems, however, you were very specific about this one, and I would be interested in the source of your claim.

  12. Pure and simple that the United States regulatory agencies and the airlines like to think they know best about everything, certainly more than Europe. Europe has no problem with it.

    What comes to mind was when European countries came out a long time ago with GSM. But, leave it to U.S. telecommunications companies to come out with competing systems, within the States: CDMA and TDMA. Just to keep customers from switching to different carriers. After much B.S. on the subject, all U.S. carriers went to GSM.

    Oh, and don’t forget Y2K, when the sky was falling.

  13. Whether the 5G issue is actually a big deal or not is irrelevant for airlines. If the FAA says it is, we’re required to follow their guidelines. So even if technically it really isn’t that big of a deal, we are stuck until the FAA says it’s good. Just like every day if there is some minor issue with a plane that wouldn’t in any practical sense compromise the safety of the aircraft. If the publication for that plane says we can’t go, we can’t. So it is catastrophic for airlines in the sense that we are limited by it if the FAA says we are, even if that limitation is ultimately unjustified.

  14. Just to clarify, the study being cited by airlines and the FAA was a *model* that suggested *some* interference and declared more studies were needed.

    The same group that sponsored that study did NOT follow up.


    Read it yourself. ZERO evidence of actual harm, just a single study with some models suggesting that certain specific altimeters (which they refused to name) MIGHT have an issue.

    The FCC has, at all steps, brought receipts. By contrast, the FAA and RTCA have absolutely refused to do so until Oct 2021. The FAA sat on their hands and did nothing but make public threats about air safety for literal years.

    Summary here: 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/

    Those espousing the views of airlines would do well to research the issue before opening their mouths…

  15. Sadly, the credibility of the US government and industry is near zero. No coordination, constant bickering and whining. These are not traits of a country that has it’s act together. The Chinese have NOTHING to worry about.

  16. The US should have used 5g in the same frequencies as the rest of the world and not done it differently. This would have solved the problem.

    As there were previously buffer frequencies for planes, the FCC should have never been able to auction those frequencies off without going through the FAA. Since it is the FCC’s fault and the agency earned billions of dollars from the auction, the agency should have been forced to use the money that it brought in to pay for the altimeters to be fixed.

  17. @Tim Dunn Could you elaborate on what you mean when you say that 5G isn’t being deployed in the same way as in other countries? The report and webcast by Airbus/Honeywell/Collins that is raising concerns as that contains a chart showing the actual frequencies for major western countries and you can see that in Canada, Japan and the UK the guard band is smaller than in the US.

    @Bill Cummings. Gary is probably depending on the report from RTCA which is raised the concerns in December 2020 and lists the frequencies allocated for 5G for a number of other countries.

    The chart that really matters is at 0:42 of RTCA’s webinar (available on Youtube) which shows that typical radio Altimeters (which operate in the 4.2-4.4 GHz band) have a receiver mask response going all the way down below 3.7 GHz (and well above 4.4 GHz although that isn’t an issue right now). In other words the altimeters aren’t filtering out frequencies well beyond their assigned band.

    One of the things first things undergraduates in electrical engineering learn in a class in radio design is the importance of filtering to keep out of band transmissions to keep them from getting to the demodulator. Assuming that there won’t be out of band signals is risky because there is no guarantee they won’t be there. While it might not have been unreasonable to not filter in order to keep complexity and cost down in 1980 when the specification for Altimeters was last updated it hard to understand how once it became known that the 3.7-3.980 GHz spectrum would come into use the altimeter makers didn’t add inline filters (which are commercial available) or update their designs.

    If someone producing FM receivers failed to filter out legal, authorized transmissions on an assigned adjacent frequency that was previously unoccupied but came into use I find it hard to see how the fault would lie with the user of the new bands rather than the radio manufacturer. Radio Altimeters are just a kind of radio receivers. The don’t have the right to spectrum out side of that which is assigned to them including a right to require that spectrum remain unused so that they can avoid filtering. The FCC could have granted altimeter manufacturers the right to the entire spectrum from below 3.7 GHz to 4.9 GHz but didn’t because allocating more than 1.2 GHz of bandwidth instead of 200 MHz just so the manufacturers could leave out filtering would be a terrible waste of very valuable spectrum

  18. @guflyer no that would not solve the problem. The report intent was to show there might be problems of interference in a very limited number of specific circumstances. It was not intended, nor did it purport to say that other countries don’t have the same potential problems. They don’t address that issue because it wasn’t relevant to raising their concerns however the information in the report indicates that at least some countries such as Canada, Japan and the UK could have problems at least as bad if not worse than in the US because the band gap between their 5G band and the bottom of the altimeters at 4.2 GHz is smaller than that allocated in the US. Uh oh.

    Keep in mind the report did not identify any instances of failures but due to the design of the altimeters (which vary and the filtering characteristics of which are unknown since there are various models in the field many of which are decades old) that the likelihood of failures in some circumstances is a a possibility. That is sufficient cause for concern since automated landing systems depend up continuous altimeter data so even a brief loss of information would be unacceptable. Hands on landing would likewise be affected because the safety systems could trigger an alarm with loss of data (“pull up”) causing the crew to scramble trying to figure out why the safety system is warning them when nothing seems to be wrong, would itself cause an unsafe situation.

    The RTCA paper (which is worth reading, as is the webcast) states moving forward that RTCA is working to develop a new radar altimeter standard which would include interference tolerance requirements, but the standard isn’t going to be ready until the end of 2022. They go so far as to state that the mid band spectrum is EXTREMELY valuable (emphasis theirs) so I don’t think there is any dispute from Airbus/Collins?Honeywell that they need to take care of the problem by providing altimeters that can co-exist with transmission in the new spectrum. What’s strange is that this is only coming up now although manufacturers have known for a long time that
    the new use was coming online. There is even a company that sells an inline filter, claimed to have the necessary certifications, so why haven’t aircraft been retrofitted? I can only guess that the airlines didn’t wanted to pay for it.

  19. @Bill Cummings the RTCA report says that the UK operates at 3.8-4.16 GHz vs 3.7-3.98 for the US however checking I see their webcast includes a chart showing the UK as operating between 3.4-3.8GHz so there is some confusion going on. But I don’t think which is correct matters because both Japan and Canada have smaller band gaps and the report makes clear that altimeters currently have no requirements for front-end rejection.

  20. Steve,
    Cranky Flier (see link in blogroll to the right) has a story today w/ graphics that explain the differences between the US and other countries, esp. France.

  21. Cranky fails to address the crux of the issue which is why altimeter manufactures decided to not include out of band filtering in first place and failed to add them when it became clear that there would be legal transmissions in an adjacent band which would disrupt their operation.

    The manufactures admit this is something they have to fix (duh). The question is why they failed update their equipment and why the FAA didn’t require them to so. As an electrical engineer I can’t imagine blaming this problem the cell companies use of these new frequencies. Perhaps it was a rational cost savings measure to allow out of band interference when there seemed to be little likelihood of it occurring but once it became obvious that these frequencies would see use it would seem pretty clear that the altimeter manufacturers where the ones who had to add the necessary filters whether the the FAA ordered it or not because in the end proper functioning of their equipment is their responsibility.

  22. @Steve: I really appreciate your comments and pointing me [us] to the RTCA material. I think [hope] that I now have a better grasp of some of the issues.

    Again, thanks.

  23. @Bill You’re welcome. Reducing tower output power and angling tower antennas downward the way the French are doing is a pretty poor fix since it will reduce the area each tower can cover and therefore increase the number of towers required without really getting to the underlying problem that the altimeters aren’t filtering out of band signals.

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