Thursday, May 28, 2020

Airlines and information

Airlines are in big trouble. Even after reopening, nobody wants to fly, perceiving them as dangerous.

But are airline flights dangerous? As I read the super-spreading literature, I have not seen a single case of an airline flight charged with spreading the virus. (Please chime in if you have seen any documented cases of virus spread on airline flights.) That's remarkable. From January to March, people were flying all over the world. People were flying from Wuhan to all over the world. But while we have seen super spreading events in restaurants, bars, cruise ships, aircraft carriers, nursing homes, jails, beach parties, Mardi Gras, choir practice, and more, I have not seen one from an airline flight. Even though people are cooped up for hours in close quarters.

One can speculate why. Airliners actually have very good ventilation systems and hospital grade HEPA filters. Except for the occasional chatty seat mate with cat videos to show, people are usually completely silent. Talking loudly seems to be a big part of spreading the virus. An airline with reasonable extra precautions, such as taking temperatures, certifying no symptoms (and you get your money back if you say you have symptoms, please), masks, wipe downs, is likely safer still. The worry may be for nothing.

But how will we know? Now I get to the point. In the tens, and probably eventually hundred or more billion dollars our government is spending to prop up airlines, how about 1 billion for research on the question, is an airline flight safe? For a billion dollars we ought to be able to answer this question definitively in about a week. Actually 10 million -- 1/1,000 of the money our government will shovel out to boost airlines -- ought to do the trick. If I'm right, that would do more good than an MMTers dream of stimulus.

This is part of a larger issue. Yes, I'd love a vaccine. Yes, I'd love widely available cheap tests and a public health infrastructure that can do something useful with test results. Well, we have what we have. But the government can still subsidize science. And it can still promulgate useful information. Yes, the airlines could pay for it, but in our politicized age nobody trusts science on logic and data anymore, they just look for who paid for it. So that won't work.

Spend 1 week and $10 million. Find out if air travel is safe or not. Tell us the answer. If as I suspect the answer is that you're about as likely to catch corona virus on an airplane as you are to die in an airline crash, then let us know.

Recovery without second wave depends on up-to-date accurate information on how the virus spreads -- and how it does not spread.


Or maybe this is a job for the FAA. After all, they seem to have the time on their hands to regulate American Airlines hand sanitizers, and air safety is their concern.

(Off topic, but I think Tyler and Gary Leff failed to see the bright side on this one. Yes, it seems a bit dumb that American Airlines has to ask the FAA to sign off on its hand sanitizers. But Tyler forgets just how bad the regulatory state can be. Yes, American does have its very own "local office of a federal agency dedicated to your business, with its own letterhead."  But that is a whole lot better than the usual -- 5 different regulatory agencies, each with 10 offices, nobody able to give a final yes, but all happy to stop a project going forward. If only there were a single office for home rehab in Palo Alto, where you can get a straight answer on anything in a week! Bureaucracy can be much worse than the FAA. )

A clarification

I response to a comment, suggesting that putting sick people on a plane might be hard to get through IRB review. I didn't have that in mind. But surely the kind of ex-post sleuthing that revealed the other super spreader events came from specific restaurants can be used. Take passenger lists of planes in January, and match them against Covid data, for example.

On flight attendants. They, like bus drivers, bear a substantial risk. Even if an airplane is not a super spreader, where lots of people get together and all have a chance of getting it, one individual who contacts many others during a day is at particular risk. However, first, this is not really the central public health concern. The public health concern is to get the reproduction rate under one. Small groups, no matter how heroic, who are susceptible, don't add a lot to the reproduction rate. Second, like doctors, they are well trained professionals. It's possible to run hospitals where doctors don't get sick. As is already happening, the main key is just to reduce contact between flight attendants and passengers. They really are there only for a crash, now sit down be quiet and don't breathe hard. Third, the point of the post is how to get people on airlines, not how to get flight attendants on airlines.

From a correspondent: quoting science magazine on Japan's experience
Not surprisingly, they found that most clusters originated in gyms, pubs, live music venues, karaoke rooms, and similar establishments where people gather, eat and drink, chat, sing, and work out or dance, rubbing shoulders for relatively extended periods of time. 
But commuter train travel reflects similar realities to airplane travel and didn't spread on Japan's commuter trains:

Reassuringly, they did not trace any clusters to Japan’s notoriously packed commuter trains. Oshitani says riders are usually alone and not talking to other passengers. And lately, they are all wearing masks. “An infected individual can infect others in such an environment, but it must be rare,” he says. He says Japan would have seen large outbreaks traced to trains if airborne transmission of the virus was possible.

A note: 

Of course there is a worry about all travel -- that's how places are seeded that have gotten rid of the virus. Nothing special about airplanes here, and in fact whatever testing and screening airplanes do may be helpful to stop that. Also if there were, for the $5 trillion we're spending, anyone in the government doing tracing, it's a lot easier to figure out who is on a plane and where they came from and where they're going than if people go in cars and RVs.


  1. I’m quite sure there is no way to get a quick and convincing answer to this question in an “ethical” way, ie. passing the IRB review. You can’t just put an infectious person on a plane with a bunch of uninflected people and see how many catch it over 10 hours flight. That would be “unethical” and you couldn’t get “informed consent” from the study participants. Anything else will take months/years instead of weeks, and will not have nearly equivalent power to convince people.

    1. I agree. I can think of a way quickly to get to a pretty good answer, at least for a specific demographic group: see if a bunch of lower-risk people (under 30? or 40?) will agree to be on a plane with some known symptomatic COVID-19 infected people.

      I understand the historical reasons that medical ethicists are uncomfortable with such experiments, but it's certainly not consistent across professions. The risk for younger, healthy people are probably on par with (or even less than) professions such as being a firefighter or driving a race car. The risk is definitely less than being a soldier in a shooting war.

      As a related topic,several people (including Alex Tabarrok) have written about the potential for Human Challenge Trials - exposing vaccinated people and a placebo group to a known infectious dose of COVID-19 - to speed testing of the efficacy of a vaccine. It's not an outlandish idea for lower-risk populations, as my understanding is that it's been done with diseases such as influenza and malaria. Apparently such trials first require "dosing studies" to test a small (also lower-risk) group to determine the dose of viral particles that result in infection. It seems like these "dosing studies" would help in evaluating the likelihood of transmission by various methods and in various environments.

    2. I think its pretty easy. Use no people. Don't use the virus. Release an airborne marker with particulate size similar to the virus in the front of the plane. Run the air handling system for 10 hours. Sample the air and measure the distribution of the marker throughout the airplane cabin. Of course this won't answer the question 100% but no experiments ever do. Seems like a good start and the basic question is spot on. How dangerous is it to sit in a sealed tube for 4 or 5 hours where the air is re-cycled continuously?

  2. I agree that we want to know more about how the virus spreads. Is it really so easy to determine that we could spend a week and $10M and get the answer with respect to airplanes? (I am skeptical, but if that's true that fact that such studies have not been done would destroy any remaining faith in US public health.)

    Re "(and you get your money back if you say you have symptoms, please)" note that the practical effect of this would be to make all fares fully refundable which would have massive effects on pricing and the industry as a whole.

  3. Hi, two comments in reply to the "are they safe" question.

    1. Flight attendants seem to have more than their fair share of infections. Sure, that might be due to other risky behavior - perhaps all the stories of their penchant for time in bars on layovers is true. :) But it might also be due to elevated risk on board.

    2. There have been a number of studies showing viral particle spread on planes. Whether that's enough to "do you in", I don't know.

    3. (sorry, I know I said two, but I'm not good at numbers) I did see a study showing actually infected people on a flight with respect to where the originally infected person was sitting. But, alas, I can't start to remember where I saw it, sometime in the last week or so, and I am not even sure if it was a Covid-19 study or an earlier respiratory virus study.

    My tentative conclusion is there is elevated risk, but I know you didn't ask for opinions, just the facts!

    Also, a related question to you in turn. I'm starting to wonder about the reality of the risk of catching the disease from a fomite. You know - I cough and the droplets fall onto a surface (fomite). Someone else touches the surface, then a while later, sticks their fingers in their mouth.

    I know it is cited as a possible infection path, but has anyone actually ever been infected that way?

    As always, thanks for your excellent posts.

  4. I agree people are wary of flying because of their fear of being confined on a (partially) closed ventilation airliner in close proximity to others seated nearby. Even though social distancing is possible, complete filtration of air is difficult if impossible. I believe the major reason people are not flying is because there is nothing to do, and nowhere to go to do it, you can do nothing staying home or you can spend money to fly somewhere, to do nothing. This should ease in the next few months and I imagine we'll see people flying around the county again. DBW, GSB XP54.

  5. How would such evidence come about? People transit through airplanes. They don't work or vacation in them.

  6. It is amazing how little money is being spent on actually figuring out how the virus spreads. I played tennis this morning, being care never to have two different people touch the same tennis ball, but also knowing that the evidence seems to be that fomite spreading is rare. Why don't we know these things? Why don't we know if it takes prolonged face-to-face exposure to someone talking/singing/screaming loudly in order to generate the viral load needed for infection? Imagine how much "smarter" our re-opening could be if we actually knew with reasonable precision the high-risk behaviors. It beggars belief that these questions are still unresolved and seemingly little researched.

  7. Dear John,

    Would it be too much to ask for your references on super-spreaders?

    Thank you.

    1. I might be wrong, but I think that this the article - certainly makes the point about no airplane events.

  8. I suspect like all the other pandemic's (1918 Spanih H1N1, 1957 Asian H2N2, 1968 Hong Kong H3n2, 1997 bird flu H5N1, 2002 Sars, 2005 to 2009 Swine H5N1 and the ZIKA) Everyone will eventually be exposed and have 1. no symptoms 2. get sick and get well or 3. Die.

    IMHO, if and when we get a vaccine in will be like all the others ... very limited in its scope. Soo, I'd like all the healthy younger people to get out and fly and develop 'herd immunity' faster. (By the way, I here motor homes and RV's are selling like hot cakes)

  9. Sovereign wealth (or debt, ha ha) CAN be deployed properly so we don't need massive Fiscal and Monetary Bazookas. But, it requires thinking and competence, which is in high demand but in short supply for whatever reason. I have my own thoughts on that but I don't want to launch into a screed.

  10. Relevant WSJ article on this topic -

    Interesting quote:

    "The International Air Transport Association, a trade group, has collected reports of crew members who have become infected on the job but said that of 18 major carriers it surveyed recently, none reported instances of suspected transmission between passengers. The survey found three episodes of suspected in-flight transmission from passengers to crew members between January and March, and four cases in which pilots might have transmitted the disease to another pilot before, during or between flights."

    Understood there might be debate on skewed information from the source, but seven flight crew are statistically a drop in the bucket that I'm fairly certain are indistinguishable from zero in overall stats. (I write what while not denying the possibility of personal tragedy. Best wishes that they all had / have a speed and complete recovery.)

  11. Good points here by Professor Cochrane, though I think he's wildly optimistic to posit that such a study could be completed in a week.

    One question, thought: I'm curious about his reference to a "beach party" superspreader event. I can't find such an event with a quick Google search, though it's certainly possible that I missed something. I think that such an event is possible - lots of people in a small area, even outdoors, talking (or singing and shouting) in each others' faces - but I haven't seen documentation that such an event occurred. The typical beach environment - outdoors, sunny, possibly windy - is a mitigant, but not an ironclad guarantee against such an environment.

    (Ski resorts, by the way, have documented cases of superspreader events, though with a good chance that the actual mechanism of transmission is a subset of "crowded indoor bars".)

  12. One of the contact tracing items that Western Australia has done is actually publish the seat numbers and plane number of people that had Covid-19 when they came into the country or found during quarantine. I have not heard of a single transmission in this fashion. All the current cases are of people in quarantine off cargo ships or airplanes that brought it with them on the plane. Otherwise this entire state is almost Covid free

  13. John, the problem is not contagion on flights. The problem is that air travel mixes people across regions and countries.

    I don’t worry about getting sick on the plane. I worry about getting stuck in a quarantine after I arrive. I worry about all the tourists coming to my small town - a well known resort area.

  14. Mr. Cochrane: I cannot agree with you.

    It may very well be true that there have been no "superspreader" events on airplanes. (I doubt that this can be definitely proved) But, it cannot be shown that NO ONE has contracted COVID-19 from another passenger (or crew member) on an airplane.

    I personally believe that I have been infected with diseases, that thankfully were not COVID-19, while riding in airplanes -- frequently. Over the past decade, I have flown about a dozen domestic and four international segments per year. It doesn't make me a goldcard patron, but I am in the game. In the years since school age children stopped living in my house, riding on an airplane has been prodromal to almost all of my respiratory infections.

    Your encomium to the ventilation systems on airliners misses a couple of important points. First, the systems are not run while the planes are parked at the gate. Second, in recent years the have been many occasions when I have been on airplanes and the ventilation has been turned off. I have been advised by crew members that this was company policy intended to save fuel, and that if passengers complained the pilot could turn the system back on.

    Thirdly. The ever decreasing seat sizes have reached a ridiculous level. I quote the following about the seats in the "Economy" section of a United Airlines Boeing 737-800 (listed on as a 30 in pitch 16.3-17.3 in. width):

    "My 8 year old, 4 year old, and I had 14D, 14E, and 14F. Thankfully they don't take up much room ... I'm a petite 5'3" woman and my knees were touching the back of the seat of the row in front. Unheard of. It was a red-eye flight to Cancun and the row in front of us reclined all the way, which left us even less room."

    I would also add the recent trend of shrinking the bathrooms. I cannot use them in a seated position. Crew Members have told me that they are really uncomfortable and hard to use. They cannot be sanitary.

    My proposal is that the FAA should impose minimum size requirements and health and safety requirements on all airplanes operating commercially in the US. I will lay this out in terms of the average single aisle aircraft operated by the large airlines in the US (Boeing 737 Airbus 320). They are typically 960 in long and 144 in wide.

    First, rows of seats should be no closer together than 40 in. and there should be a minimum width of 21 in. There would be no more than four seats across with an aisle between them with a minimum width of 36 in. The seat backs should extend at least 9 in above the top of the seat cushion The upper part could be clear to avoid claustrophobia and to allow crew members to see what is going on. There should be a barrier between adjoining seats extending 12 in from the seat back. The barrier should be moveable so that parents could attend to children and so forth. Seats should not be allowed to recline back. They can have mechanisms that slide the bottom forward and allow the back cushion to recline.

    Currently with 30-32 in pitches, and 17 in wide seats. These planes often have 30 rows of six seats or 180 seats. In my system there would be 24 rows of 4 seats or 96 seats. Fares would have to double.

    But crews could be a little smaller. And, people would feel better about flying when they do scrape up the fare. So they might be more inclined to fly.

    In my view we have been running an externality of disease costs to subsidize airplane fares. We should end it.

  15. Let's use some common sense. How did the virus get from Wuhan to Milan, and New York City?
    Did it travel by boat? By car? Maybe it took the train?
    The only plausible answer is that it traveled by plane.
    If there are no super-spreader events on planes it's because the healthy, wealthy globe-trotters who spread it were far less likely to be in the at-risk groups. They were likely asymptomatic, or had mild symptoms, and they traveled the world spreading the disease.
    It's a Davos-hating populist's dream.

    As a rertired airline's captain matched with an active flight attendant wife,I would submit---and certify-- that the terminals and aircraft are more sanitized than ever before. Lots of comfortable seating space and crowds are light. It won't last!

    1. The fact that somebody says something that in your opinion is silly, does not give you the right to call that person stupid. I agree that he may have not gotten the point, which is whether spreading happens on planes or not, but that doesn't allow anybody to call names...or at least we should do our best to avoid calling names. Our society is going south with so much hatred. It's up to us to correct that, and each of us can contribute to a better and more respectful society -- which will happen when we can listen and treat with respect everyone, even those who don't think like us.

      On a separate note , great post, John!

  17. Sounds like a call for a version of the Michelson–Morley experiment to that was devised to prove the existence of the luminous aether, and failing to find evidence of the aether's presence opened the way for Einstein's theory of special relativity.


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