Some American airlines have raised the ante for describing how safe it is to fly during the pandemic. United Airlines claimed the coronavirus risk is “nearly nonexistent” when passengers wore masks even on its full flights. Southwest Airlines claimed the coronavirus risk is “virtually nonexistent” on its planes. The airlines argue that modern filters and universal masks have now reduced the transmission risk to almost zero. To say the least, however, these assertions are very highly overstated.
The airlines discuss exercises with dummies on widebody jets, which have suggested the transmission of the coronavirus is minimal. But they do not mention recent papers in medical journals that report the cases of actual passengers. One such paper discussed a Vietnamese flight from London to Hanoi on which a woman with the coronavirus infected almost a dozen business class passengers within two meters of her.
Another told of an Australian flight from Sydney to Perth as passengers with past coronavirus infections caused eight new infections on board. Yet another paper cited an Israeli flight from Tel Aviv to Frankfurt where two passengers contracted the disease. Another paper considered two rescue flights from Italy to South Korea, in each of which one passenger contracted the coronavirus. All of these planes have modern filters and show the transmission is reduced but not eliminated.
The best research on the effectiveness of masks is the analysis of several studies about transmission and estimated that masks reduced the chance of infection by 66 percent. The passengers on the Vietnamese, Australian, and Israeli flights did not wear masks, so such effectiveness noted by the analysis would have reduced new coronavirus cases on these flights from around eleven to four, eight to three, and two to one.
But the passengers on the Korean flight wear medical grade masks with greater protection than cloth or surgical masks. Since several infected people boarded these flights, it is likely the number of new coronavirus infections would have risen from one to five or more with such cloth or surgical masks worn in general across American flights.
The airlines have also cited a paper that found 42 confirmed coronavirus infections among the over one billion passengers who have flown in 2020. But large numbers of passengers flew before the coronavirus decimated travel. In the United States, there were more passengers who flew then in January and February than over the next six months total.
In the countries like China that are closest to regular flight schedules, the coronavirus has been all but eradicated. Moreover, the authors conceded the majority of infections on planes may never have been confirmed. One of the authors refused to take part in a presentation of the findings since he believed this key point had been improperly devalued.
The many uncertainties over the coronavirus on American flights could be resolved with trustworthy data around what happened on them. But such reliable data are virtually nonexistent. American protocols have in general been so weak that we have scant information about how many infections arose in what settings. How many Americans have become infected while riding on public metros? Or while dining at restaurants?
The only cases we know much about are events in which huge numbers of people contracted the coronavirus at the same time. But transmission on planes would not produce such events. Further, we know very little about which passengers with primary infections boarded planes, still less about which passengers became infected on board, and almost nothing about coronavirus infections which trace back to aircraft cabins.
Under conservative circumstances, the risk of catching the coronavirus on American flights that are 75 percent full is not zero but one in several thousand. These infections would result in about one death per million passengers. By contrast on American flights, crashes cause about one death per 34 million passengers. The greater majority of these victims would be people who were not even passengers on board.
American airlines are financially desperate. They are trying to make their planes safe for passengers. But they have no excuse for making difficult promises about the “nearly nonexistent” coronavirus risk.
Arnold Barnett is the George Eastman management science professor at Massachusetts Institute of Technology. He conducts research in aviation safety and has a White House citation from the Flight Safety Foundation.