Airlines are using studies on COVID-19 spread to justify filling middle seats, but critics say the science isn't so clear

• Several studies that suggest flying is safe during the coronavirus pandemic have come under criticism in recent days.
• While all evidence suggests the risk of contracting COVID-19 while flying is relatively low, it still appears to be possible.
• Southwest cited two of the maligned studies in its decision to stop keeping passengers from booking middle seats.

Southwest Airlines on Thursday said it would stop blocking middle seats on flights, citing several studies that suggested the risk of catching COVID-19 on a flight was low.

Southwest joins American and United, leaving Delta the only one of the four biggest US airlines to limit capacity on flights to facilitate a degree of social distancing.

Airlines are caught walking a delicate line between providing — and promoting — safety on board, seeking to both prevent travel demand from collapsing again while cutting costs everywhere they can. Of the measures airlines can implement to try to protect against the virus, blocking middle seats is one of the costliest.

Though some evidence suggests the risk of COVID-19 transmission on airplanes is indeed low — for instance, flight attendants have lower rates of the virus than the general population — recent studies have come under criticism as airlines rush to tout the results as evidence that flying is safe.

One of the biggest studies — and the study that Southwest cited most heavily — came from the Department of Defense, which found that the chances of catching COVID-19 on a flight were "very low," as long as those on board wore masks.

Though the Defense Advanced Research Projects Agency, which ran the study, is generally viewed as a reliable source, the study was cosponsored by United Airlines and Boeing, introducing a potential conflict of interest. That involvement has opened the door to skepticism, with one well-known virologist writing on Twitter that Southwest had made a "bad call" by relying on it.

Moreover, several aspects of the study affected its usefulness. For one, it was performed on larger wide-body aircraft, rather than the narrow bodies being used to fly most domestic routes today (and which Southwest flies exclusively). Also, it did not account for passengers removing masks during flight — even passengers who comply with the airlines' mask requirements may still remove them to eat or drink.

Southwest did not immediately respond to a request for comment regarding criticism of that study.

In a separate presentation, the global trade group International Air Transport Association said it had found just 44 instances in which the coronavirus might have been transmitted on flights among roughly 1.2 billion travelers. That would be one case for every 27.3 million passengers.

That conclusion, however, was swiftly rebuked by one of the scientists whose research was drawn upon for the study. The infectious-disease specialist Dr. David Freedman said he had declined to participate in the presentation, citing "bad math."

Moreover, several studies suggest that COVID-19 can indeed be transmitted on airplanes. One relatively controlled contact-tracing study that found a passenger had acquired the virus during a flight in which all passengers wore a protective N95 mask; she removed hers to eat and left it off for several minutes as she used the lavatory.

Earlier this summer, a statistical model from a researcher at MIT found that while the overall risk of contracting COVID-19 on a flight was low, filling the middle seat doubled that low risk.

To be sure, while the science is inconclusive, airplanes appear safer than other indoor, close-quarters settings. And as airlines report record consecutive losses for the third quarter, they're desperate for anything that can cut costs and bring people on board.

Southwest, for instance, posted a $1.2 billion loss — its highest ever — for the third quarter. Airline executives said it lost $20 million by limiting capacity on airplanes.

But even if the airlines could prove conclusively that flying is safe, it may not matter.

Travel demand remains down 65% to 70% over 2019 levels and — with the exception of a few outlier days — is holding steady. Travelers will not flock back to the air until there are places to go and things to do, airline CEOs have said.

COVID-19 cases are spiking around the US and the world, and a bunch of states have quarantine requirements for incoming travelers. Moreover, many destinations remain at least partially closed. Theaters in New York City will remain shuttered until at least mid-2021. The city's restaurants are operating at 25% capacity, and cold weather will presumably nix eating on sidewalks and patios. California's theme parks remain closed; Those in Orlando, Florida, have limited capacity. The bars, shops, museums, and other attractions that lead people to travel for fun simply aren't available.

Most business travel, meanwhile — which typically makes up just 15% to 20% of the big three airlines' passenger loads, but 50% of their revenue — is on hold. Big events like conventions won't happen anytime soon, and companies are unwilling to risk their employees' health or the liability, not to mention the expense of business travel in a weakened economy.