Using these and other measures as part of a layered approach could push the risk of catching the virus on a plane below that of other activities, including grocery shopping and eating at a restaurant, researchers at the Harvard T.H. Chan School of Public Health concluded.
“Though a formidable adversary, SARS-CoV-2 need not overwhelm society's capacity to adapt and progress,” the report said. “It is possible to gain a measure of control and to develop strategies that mitigate spread of the disease while allowing a careful reopening of sectors of society.”
This study, from the industry-funded Aviation Public Health Initiative, is likely to be cited by airlines and plane manufacturers as they continue to try to convince the public that it is safe to fly as long as proper precautions are taken.
The Harvard study follows the recent release of a Defense Department study that concluded that wearing a mask continuously while flying could reduce the spread of the virus because of how air is filtered and circulated on an airplane. Along with previous research, the two studies further bolster the case for wearing face coverings. The Centers for Disease Control and Prevention also recently updated its guidance on face coverings to say that it “strongly recommends” that masks be worn on all forms of public and commercial transportation.
The Harvard team included experts on environmental health, industrial hygiene and infectious diseases whose goal was to develop a “comprehensive understanding of the intersection between the science informing SARS-CoV-2 transmission and the operations in the aviation environment.”
In this instance, they focused on strategies to protect people during what they called the “gate-to-gate” part of their journey. A second study, expected in early 2021, will look at the science and recommend strategies to safely manage the “curb-to-curb” portion of a traveler’s journey.
It is being funded by airlines, airports and aircraft manufacturers.
Leonard Marcus, founding co-director of the National Preparedness Leadership Initiative, a collaborative effort of the Harvard School of Public Health and the Kennedy School of Government, said that the industry’s involvement with the study did not influence the team’s findings.
“There were open conversations back and forth and we were very adamant about maintaining our independence,” Marcus said. “We felt that the lines were drawn well enough for us to conduct our independent research.” He declined to say how much the study cost.
Since the pandemic began, many have viewed air travel with suspicion in part because it places people in an enclosed space with others for a significant amount of time — behavior that runs counter to much of the guidance from health officials.
The CDC, for example, continues to caution that air travel presents some risks because of those factors.
Researchers have identified examples where the virus may have been transmitted while travelers were on board an aircraft. In one instance, a woman flying from London to Hanoi in March appears to have infected as many as 15 other passengers and crew members. In another case, researchers in South Korea think a woman may have been infected after she removed her mask while in the lavatory.
Although the cabin of an aircraft may not lend itself to social distancing, Harvard’s team found that current aircraft are equipped with onboard systems that constantly circulate and refresh air, which can compensate for the lack of space.
“This level of ventilation effectively counters the proximity travelers will be subject to during flights,” the study’s authors said. But an airplane’s ventilation on its own isn’t enough.
“The level of ventilation provided onboard aircraft would substantially reduce the opportunity for person-to-person transmission of infectious particles, when coupled with consistent compliance with mask-wearing policies,” the study said.
Airlines could further boost the effectiveness of those systems by continuing to run them even when the plane is parked. In July, United Airlines announced that to maximize airflow through the cabin, it would keep its filtration systems running during the boarding and deplaning.
Although much attention has been focused on what happens aboard an airplane, the study also examined another key element of a trip: how passengers board and deplane an aircraft.
“We go to the grocery store and there are lines about where you stand and with few exceptions, people obey them,’’ said Edward Nardell, an associate professor in the Departments of Environmental Health and Immunology and Infectious Diseases at the Harvard School of Public Health. “We need them to do the same on the jetway. We’re so used to piling up there and we need to make that stop.”
One strategy would be to admit small numbers of passengers in a row-by-row sequence, so people could stow their luggage and take their seats before other passengers board.
Researchers also emphasized that travelers need to take responsibility for keeping themselves and others safe. People should be mindful of others when eating and drinking on a flight, perhaps taking turns to ensure that not everyone has their mask off at the same time or using straws to sip beverages. Instead of relying on flight attendants to remind people to wear their masks, individuals could remind their fellow passengers about the need to do so, researchers said.
“The findings and recommendations in this report offer the public the opportunity to reach informed decisions about air travel,” the report said. “There is much to gain by simply following the science. It offers a bounty of information about how people can achieve both public health safety and opportunity.”
Airlines for America, a trade group which provided financial support for the study, said major U.S. airlines have already adopted many of the strategies outlined in the report.
“We are encouraged by the results of the independent study... as this is the first comprehensive research to evaluate the entire inflight experience,” said Katherine Estep, an A4A spokeswoman. “The research concluded that there is very low risk of virus transmission on airplanes and that the multiple layers of protection against COVID-19 make being on an airplane as safe if not safer than other routine activities, such as grocery shopping or going to a restaurant.”