Why You Should Keep Wearing a Mask on Planes—Even When You No Longer Have To
For more than a year, a mask has been as essential at the airport as a boarding pass: you can’t fly without one. But the federal mask mandate for planes, trains, buses, and transit stations including airports is set to expire on March 18, and so far, the government has not announced plans to extend it.
That could change. The Transportation Security Administration has extended the face mask requirement several times so far. But as Omicron cases decline nationwide and states drop their own mandates, it’s not clear whether the policy will be renewed again. The U.S. Centers for Disease Control and Prevention on Feb. 25 relaxed its own guidance around masking and currently says indoor masking is not necessary for about 70% of the population. Though that guidance is separate from the travel mandate, it signals a growing acceptance for going bare-faced.
For months, airline executives have questioned the need for in-flight mask mandates, arguing that the air filtration systems on planes are effective enough to eliminate virtually all airborne pathogens. Representatives for the nation’s largest flight attendant union, however, have said they expect the mandate to be extended, since COVID-19 is still circulating widely and young children remain ineligible for vaccines.
It’s not clear yet whether the Biden Administration will extend the transportation mask mandate. But here’s what the research says about wearing masks on airplanes.
How dangerous is flying during COVID-19?
Throughout the pandemic, there have been documented instances of SARS-CoV-2 (the virus that causes COVID-19) spreading on planes.
Still, in-flight transmission happens less frequently than one might expect with such close quarters and shared air. The authors of a research review published in September 2021, which analyzed 18 prior studies on in-flight spread of SARS-CoV-2, concluded that “transmission of SARS-CoV-2 can occur in aircrafts but is a relatively rare event.”
A 2020 study conducted for the U.S. Department of Defense—and carried out by researchers from Boeing and United Airlines, among others—found that aircraft ventilation and filtration systems reduced the risk of airborne SARS-CoV-2 exposure by more than 99%. But the study didn’t account for other modes of transmission, such as direct exposure to larger respiratory droplets expelled by an infected person sitting nearby. It also did not consider the effects of walking up and down the aisles or interacting with other passengers.
It’s hard to say exactly how risky it is to fly during the pandemic, because lots of variables affect whether SARS-CoV-2 jumps from one traveler to another: everything from how much virus a traveler is carrying to the length of the flight and the vaccination statuses of other people on board. Research has shown that risk even changes depending on whether an infectious person is talking—and therefore expelling more respiratory particles—or just breathing.
The flight may not even be the riskiest part of a trip, adds Dr. Aisha Khatib, who is chair of the International Society of Travel Medicine’s Responsible Travel interest group and has studied SARS-CoV-2 transmission on flights. (The International Society of Travel Medicine’s members include travel industry employees, as well as researchers and medical experts.) There’s plenty of potential for exposure in the airport, such as when people remove their masks to eat or drink at the gate, she says. That alone makes wearing a mask a good idea while traveling.
Should I wear a mask on a plane?
Right now, it’s required. But you might want to continue masking up on planes even if the mandate expires. Research has shown that wearing a mask in public indoor spaces reduces your risk of later testing positive for COVID-19.
On planes, the air is frequently filtered, which helps keep the risk of in-flight transmission fairly low, Khatib says. But that risk drops even lower, she says, when good ventilation is accompanied by precautions including masking, symptom screening (like pre-flight temperature checks), and social distancing.
In a paper published in March 2021, researchers developed a model for predicting the infection risk aboard a plane. The most extreme scenario they considered was a 12-hour flight in which passengers were not wearing masks and one infected person was seated in tightly packed economy class. Under these conditions, the authors estimated that other economy passengers had an average infection risk of up to approximately 11%—but for someone seated in very close proximity to the infected person, the risk could rise to 99.6%.
If everyone onboard wore a surgical mask, the average risk of infection dropped as low as 3%, the authors added. Importantly, this scenario did not take into account the benefits of vaccination, which likely reduces the transmission risk further—but the findings do suggest that masks can add an extra layer of protection on flights.
Another modeling study, published in December 2021, tried to find the best airplane seating arrangement to reduce viral transmission, again by using simulations of airborne spread. If someone on a flight has COVID-19, you obviously don’t want to sit next to them, but you also don’t want to sit behind them, the researchers concluded.
“You have to look at not only east-west transmission, but also north-south transmission,” says co-author Sheldon Jacobson, a computer scientist at the University of Illinois at Urbana-Champaign who studies public health and aviation security and has received funding from the U.S. Air Force Office of Scientific Research. Keeping middle seats open and leaving some rows empty was the safest seating arrangement, his team concluded. (Airlines, however, are no longer selling flights at reduced capacities.)
Regardless of seating arrangement, masking reduced the chances of transmission onboard by about 30%, according to his team’s model.
Of course, theoretical calculations don’t always hold up in practice. In the September 2021 research review that looked at real-world studies of viral spread on planes, the authors concluded, “It is not clear whether the use of masks can prevent transmission of SARS-CoV-2 in flights.” That doesn’t mean masks do or do not work—only that published studies haven’t fully answered the question. It’s also worth noting that all of the studies in that review were published before the emergence of the highly contagious Omicron variant.
Still, some real-world data suggest that masks work on planes. “If you look at the studies, most of the in-flight transmission…occurred in flights earlier than March 2020, prior to the enforcement of in-flight mask-wearing policy,” Khatib says.
Does wearing a mask on a plane help if no one else wears one?
Khatib says the federal travel mask mandate probably should be extended again, but it remains to be seen whether that will happen. “Given that we’re still coming off a huge Omicron surge” and that there have been reports of a new, related variant, “it does seem a little bit premature to lift these mask mandates,” she says.
Even if the mandate expires, Khatib says she will continue masking up on flights. Jacobson says he will do the same. Highly protective masks, such as N95s and KN95s, can filter out almost all particles when worn correctly, so they can help keep the wearer healthy even if those around them are unmasked.
Some survey data suggest that many people will keep wearing masks, even if they are not required to do so. In a May 2021 survey conducted by the International Air Transport Association, 83% of people said they favored masking on flights, even though the majority of respondents said they did not want mandates in place forever.
Regardless of what happens at the policy level, Khatib emphasizes that no one should travel while symptomatic, and recommends that passengers “wear a protective mask that fits well and you’ll wear consistently.” An N95 or KN95 is the most protective option, but if you find them too uncomfortable to wear for long periods of time, choose a surgical or cloth mask you’ll keep on, she says.