New Studies Reporting Covid-19 Transmission On Planes Are Good News!

Air travel spreads the virus. People with Covid-19 travel from one place to another, bringing the virus with them. That may not matter much when the virus is already spreading within the community at the destination and they’re beyond the containment stage. But early in the pandemic it’s how the virus traveled from one place to another.

That’s different from the extent to which the virus spreads from person to person while on the aircraft. We’ve known since early on that it happens, but it’s rare, primarily because of hospital grade air filtration.

However, there’s reason to believe that there has been some spread on three specific flights:

Often when we point to people who supposedly ‘got the virus on planes’ it turns out to be just as likely that they were exposed to the virus in the gate area or jetway. That is an importance difference because it suggests handling the issue in different ways, and tells us something about where risk is and what tactics are protective.

The CDC last week released a study declaring risk of inflight transmission of the virus, based on an investigation of the London Heathrow – Hanoi flight that we’ve known about for months. This isn’t new, despite it hitting the news broadly now.

Their caution is that as more long haul flights take place the virus could spread more. Singapore – Hangzhou is the length of a cross country flight in the U.S., so if the virus spread on that flight then ultra long haul isn’t necessary for spread. And they don’t explain why HEPA filtration would work less well on long flights. Longer exposure might create more close interactions but it isn’t obvious that’s the case either.

And much less reported is that the study notes no spread from symptomatic individuals on a 15 hour flight from China to Canada, and flights from China to France and Thailand. The lack of inflight spread from infected individuals is less telling, though, than it might be because most people who catch the virus don’t spread it. A small number, perhaps 10% of cases, are responsible for 80% of spread.

Nonetheless documenting just a handful of cases where inflight spread may have occurred is significant as an argument for the safety of flying because there’s never been a virus studied as extensively and intensively in a short period of time as this one. There are millions of people flying throughout the world week after week during the global pandemic, yet we haven’t been able to identify more flights where the virus spread (though there are probably some). This is highly suggestive that inflight spread is very rare.

Contrast that with recent CDC findings that spread of Covid-19 is linked heavily to dining in restaurants. Indoor activities are conducive to virus spread because the virus becomes aerosolized and viral loads build up the longer an individual shedding the virus spends in the enclosed environment. Restaurants generally lack the filtration and outside air exchange of planes, which is why air travel is much safer than indoor dining.

Meanwhile the most common response to the CDC-promoted study of that London – Hanoi flight is that it (and other identified flights where spread may have occurred) is that they were pre-mask wearing. That’s true, and 50% effective masks can reduce viral load exposure 10-fold. I think the better argument is the rarity of spread, which is consistent with the finding that airline employees have lower Covid rates than the general population despite repeated exposure across a large number of flights.

In reporting this new study, what the news isn’t telling you is how much of an outlier spreading events on planes actually are.

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, 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 interesting to see Jon mentioning that the timing here is influenced by a willingness of American’s flight attendants union to serve drinks in economy. That’s always been a part of their job, Covid-19 spreads largely via aerosols (serving a drink isn’t going to be high risk), and planes haven’t been significant vectors of virus spread. […]

  2. […] Some Covid-19 spread happens during air travel with a billion people flying so far this year it would almost be impossible for it not to. It’s never clear whether infections happened in the gate area, during boarding, or on the plane. But it’s striking how few instances have been found. Here’s a systematic look that takes advantage of testing regimes to identify instances of spread. I don’t think there’s actually enough to support masks as the reason why spread is limited though. […]


  1. This study states in many places that they can’t figure out if others got the virus from flying due to the US’s lack of good contact tracing. They use these examples where they CAN contract trace as a warning. There really shouldn’t be a way you can twist this as GOOD news for the public. Sure, filters DO help, but claiming that flying is safer than NOT flying is doing a disservice.

  2. @Bob – if you think anything I’ve said here is wrong, articulate what it is. This is very relevant to travel and I believe also quite correct. I welcome criticism and challenge, but show your work!

  3. @ Gary — The studies should at least serve as a reminder (and you should remind folks as well) that people with severe underlying conditions should avoid unnecessary travel by air until case counts are dramatically lower than today. Even then, masks should be worn by said individuals. It is easy for people to be lulled into a false sense of safety, but those with underlying chronic health conditions need to BE PATIENT! Travel will return eventually. Right now, stay home and vote Orange Hitler out of office. That is the more important than a vaccine…

  4. @Marv – this is a story covering the study that I’m writing about in this piece, linking to the study itself and citing what the researchers actually said

  5. @Gene – depending on health conditions and age, there are people who shouldn’t go to the grocery store let alone travel.

    I don’t think Trump is as relevant to Covid outcomes as many believe

  6. @GareBear – I hear ya but my point in posting that article is to show how dangerous it is to be flying right now, especially long haul. “6 Ft rule” is nonsense, as is “temperature screening”. Eating indoors in a restaurant and flying, with other risk takers, are literally the two most dangerous activities you can be doing right now.

  7. Hi Gary, just because Canada China flight had no known spread, it doesn’t mean it wasn’t there as Canada had strict criterias that time to test and people could just be asymptomatic but still pass it on to others. Unless there is universal swabbing before and after and close tracking of passengers for a few days, any conclusion is hard to draw.

    – Covid ward physician reader in Canada

  8. “I don’t think Trump is as relevant to Covid outcomes as many believe”

    Gary, gotta disagree with you there. There are many many examples of where the CDC and FDA have been hamstrung, worked around, etc. in their traditional role of managing a response to infectious disease.

    Personally I think the single biggest error made was that Trump has never been fully behind the masking protocols once their efficacy was more clearly established. If he has been more forceful about mask wearing in early April, when the CDC guidance changed, and said over and over “Listen, this is important, I know it’s not comfortable, but wear a mask when around others, it will save lives”, there would not be such continued resistance to it. The lack of mask wearing in the south and southwest and now the midwest has pretty clearly been a major part of the ongoing spread after the first wave in March-April.

  9. @DCJoe – the biggest failures in the government response have been made by FDA and CDC, as I’ve written about extensively. There’s no question that meddling by the administration hasn’t been helpful. But it’s also the case that a virus is going to virus. If you look at US policy after the earliest stages (when the CDC test didn’t work and FDA woouldn’t approve private tests, and the CDC blew implementation of travel restrictions) the biggest failure was not protecting elderly in nursing homes especially in the Northeast (and Cuomo points the finger away from himself and at the CDC). There’s a resurgence in Europe…

  10. Meanwhile in Realville, people are returning to travel despite what the ninnies are saying. I came off a 13 hour long haul originating from the US that had very few empty seats. The agent at the counter told me that’s a pretty consistent load for the month, on this daily flight. Sure it’s a small sample and while things are far from normal, I think more and more people are seeing this for what it is and making a decision that they can safely travel. Why this so upsets some people shouldn’t be a real mystery if you pay any attention to current events.

  11. Gary, I appreciate the dispassionate analysis. To do good risk assessment and make good decisions for ourselves we need information. What this study says is that if there is a risk of COVID in flying it is very tiny indeed compared to other risk factors. I don’t need risks to be zero in order to travel, or I certainly would not have done many of the crazy things I have done in my life, and hope to get back to doing before long. I do want to know what the risks really are or aren’t, and that is something the media isn’t good with. If one person gets COVID on a flight the media will go with the big headlines. If tens of millions fly safely nobody will mention it. I believe in wearing masks. I believe in social distancing when the HEPA filtration isn’t what it is on aircraft. I believe in washing my hands regularly. I don’t believe in being paranoid about flying because of a handful of possible cases over six months.

  12. Gary- agreed that Cuomo has a lot of blood on his hands for the way he handled nursing homes in NY.

    As for CDC, the testing failures were incredibly destructive to their credibility. And the Administration sent quite the message with stuff like this in late February.

    The decision by the Administration to halt USPS distributing masks in early April is especially galling.

  13. @Andrew – no one said “it’s all safe now”

    As for where the trip reports are please convince Singapore to let me in I want some chili crab. Malaysia would work, too, for some good prawn mee soup.

  14. DCJoe is right. I don’t know what the heck Gary is talking about. Trump is unquestionably almost solely to blame for the horrid Covid outcomes in the U.S.. The biggest failure is POTUS fails to take responsibility for organizing and implementing a national response to the virus. He mocks wearing masks, threatens governors and other public officials who have taken responsibility and implemented measures that control spread, encourages people to ignore those measures and have them lifted prematurely, and doesn’t require social distancing or mask wearing at his events. Because SARS-CoV-2 is immune to lies, flattery and bullying our feckless leader is at a loss to deal with the virus and instead must rely on his ability to confuse, distract and pretend everything is just fine.

    Experts have said universal mask mandates would save tens of thousands of lives! Trump himself admits to playing down the severity of the virus because he didn’t want “panic.” Gary’s attempt to absolve Trump by blaming the FDA and CDC is typical Trump logic. It is like a CEO claiming no responsibility for poor corporate performance and blaming failures by his production and marketing departments. To the extent there were failures, Trump has done nothing to improve those departments. On the contrary, Trump and his political operatives keep hamstringing their ability to be clear and honest about the pandemic and measures needed to control it better.

    I am appalled that Trump and many readers of this blog are threatened by the phrase “Black Lives Matter.” In actuality, as the American death toll soars past 200,000, when it comes to loyalty to Trump, these brainwashed people don’t even believe that “White Lives Matter.”

  15. I have zero desire to ‘absolve’ Trump, but the course of the virus and outcomes don’t seem to track much with policy decisions on a cross-country basis.

  16. Yet another confirmation that discretionary travel is absolutely stupid if we want Covid to be under control.

    Lots to learn from countries that are doing a great job in protecting people don’t allow idiots like this blogger to “let me in I want some chili crab”: Singapore’s last death was months ago, they are averaging 1 new case (outside of quarantine or isolation) per day, and life is back to normal with exports 7.7% higher this August than last year’s.

  17. @Gary, I strongly (Trump adverb) disagree with your statement that “the course of the virus and outcomes don’t seem to track much with policy decisions on a cross-country basis.”

    Without doing a mountain of research, I think there can be no doubt that countries have experienced clear differences in outcomes based on governmental policy decisions and actions. We need look no farther than the differences in outcomes between China and the U.S. But even democracies have done much better than the USA. Off the top of my head, Hong Kong, Taiwan, South Korea, New Zealand, Singapore, have all done outstanding work in limiting the spread of the virus and the death toll. I believe that in many of those places, immediate acknowledgement of the problem and early action (one key action being widespread testing and tracing which Trump doesn’t like because it makes him look bad) even saved their economies from being devastated.

    In comparison, governments with leaders who stuck their heads in the sand and tried to pretend the virus was a “hoax” have suffered horribly. The U.S., Brazil, and Russia head that list.

  18. @John, probably the most comparable country in several important ways is Canada.

    Cases per million- U.S. 21,135; Canada 3,799
    Deaths per million – U.S. 616; Canada 244

    Perhaps Canada provides some sort of indication as to how much of our crisis has been due to mismanagement and how much was likely inevitable.

  19. RE: USPS masks – so we send 660m masks out and short change medical workers? I tried buying masks in late Feb/March and either OOS or proceed insanely. I spent $20ea on UV active masks (spandex) off Amazon and it took 2-3 weeks for delivery.

    It seems like thousands of people on social media
    were sewing cloth masks for frontliners.

  20. @DaveS, great point! Canada just extended its ban on visitors from the U.S.
    The way things are going, Canada will build a wall and make the U.S. pay for it.

  21. On a red-eye from ANC this week the FAs felt it was safe enough to de-mask – after the lights went down.

    It was mid-flight almost 4AM lights in cabin were off most PAX probably sleeping but still they were constantly checking for PAX and quicky pulling mask up and down on to chin –

    NO, they were not eating, just chatting away which was extremely annoying esp on a red-eye, if your trying to sleep and the FAs are louder than the cabin and engine noise that its keep you awake.

    I understand pilots not wearing mask on flight deck because they have to clearly communicate with ATC. But FAs?

  22. Dude, Gary, look at Figure 1 in the study. The whole business class cabin got COVID… ??? How you read that as good news is beyond me.

  23. For me, the full process of taking a flight has a number of phases:
    1. Taxi to airport
    2. Security lines.
    3. Sit in gate area.
    4. Stand in line for ticket scan to enter jetway.
    5. Stand in line in jetway.
    6. Aircraft on ground not running full air circulation while people mill about trying to stash carryon luggage.
    7. The flight itself.
    8. Aircraft is back on ground, at the arrival gate, not running full air circulation while people pack the aisles as they grab their carryons and try to deplane.
    9. Taxi to hotel or other destination.

    @Gary keeps doing posts about how safe #7 is while ignoring the other phases of the process, some of which have little or no social distancing and certainly poor air circulation. I think I’ll avoid flying for a few more months.

  24. Gary here is where you *could* add value on the Hanoi paper. Any idea whether the entire infected business class cabin was on a dedicated bus for a bus gate? That would help absolve the flight.

  25. @Charlie

    I was think the exact thing #6&8. No HVAC while at gate = No HEPA filters

    What good do the HEPA filter do if the HVAC isn’t powered by an *APU while at gate.

    *aircraft auxiliary power unit (APU)

    At the gate is also when people are most active and passive and breathing the hardest.

    Can’t imagine sitting on a plane an extra 30-45+ for equipment issues or ATC delaying us [sic] without HVAC during COVID.

  26. It’s quite comical how people are supposed to keep far apart from each other everywhere, including the airport. The security area, the gate area all are labeled with areas where people have to keep distance from each other. Even within the jetway. Yet…they sit shoulder-to-shoulder in a tight densely packed confined small space. If people were to walk through an airport in formation as they are on the plane and the distance they are in inside the plane, people would freak out. What makes it more ‘comical’ is that people are under mandate to keep distance while inside a large building such an airport with high ceilings, but it’s totally fine to sit practically on top of each other in a tight small space.

    Don’t sit next to anyone in a restaurant. Keep distance at the grocery store. But it’s totally fine to sit right next to a stranger for several hours in a small space. This could only make sense this year.

  27. @DaveS — And if you compare Canada to Japan, Canada has done a terrible job with COVID. But this analysis is foolish. The reality is that mankind has so far been able to do NOTHING to stop this virus. Some places are more naturally immune to it than others, but there is zero evidence that any gov’ts actions have stopped the virus. And, of course, we’re not yet at the end of the scourge, so we don’t know which countries will do the best in the end. Right now, the winner looks like Sweden: like everyone else, they did nothing to stop the virus, but have seemingly managed to achieve herd immunity with the lowest societal cost.

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