Air travel — a staple of pre-pandemic life that took one of the hardest hits when the coronavirus began to spread — still raises many concerns for people worried about catching COVID-19.
Yet more are willing to return to the skies as the holidays approach. United Airlines said the company is expecting to see last-minute bookings up 40% compared to last year and they've added 1,400 flights to meet demand.
"We expect that the week of Thanksgiving is actually going to be the busiest week at United Airlines since the onset of the pandemic," Josh Earnest, United Airlines senior vice president, told TODAY.
Months after the crisis began, travelers are flying in greater numbers as airports and airlines take all sorts of measures to reduce the risk of transmission.
More than 836,000 people passed through Transportation Security Administration checkpoints on Nov. 9 — almost 10 times more than on Apr. 14, when the lowest number was recorded during the pandemic. (But that’s still about one-third of passenger volume seen on the same day in 2019.)
Some state officials are reassuring the public that it’s safe to fly, citing the lack of coronavirus cases connected to airlines.
"The evidence is the evidence and I think it is something that is safe for people to do," said Florida Gov. Ron DeSantis in August during a roundtable discussion with aviation executives at Fort Lauderdale-Hollywood International Airport.
“You have just not seen airlines lead to outbreaks.”
'Not as risky' as people think
So how safe is air travel now when it comes to COVID-19 transmission? The Centers for Disease Control and Prevention still warns travel increases a person’s chance of getting the disease, noting that social distancing is difficult on crowded flights.
United Airlines and the Department of Defense recently teamed up on a six-month study that found the risk of contracting COVID-19 on commercial flights was low when passengers wore masks for the entirety of the flight. The highest risk was associated with sitting in the same row, or a row in front of or behind, an infected person. This study didn't take into account the risk associated with being in a crowded airport or boarding a flight.
Experts were cautiously optimistic about air travel.
“In general, I think that flying is not as risky as most people perceive it to be,” Dr. Amesh Adalja, a senior scholar at the Johns Hopkins University Center for Health Security in Baltimore and a spokesman for the Infectious Diseases Society of America, told TODAY.
“People often think of planes as major vectors for transmission, but overall, we have not seen much data on transmission on a plane, except for people that are in the immediate vicinity of that person… We've not heard about major outbreaks on airplanes.”
There have been no confirmed cases of COVID-19 transmission on U.S. flights, said Katherine Estep, a spokeswoman for Airlines for America, an industry trade group that represents major North American carriers, in a statement to TODAY.
The International Air Transport Association, which represents carriers around the world, pointed to a report that noted an "apparently low rate of in-flight transmission," but also acknowledged little research has been published on the subject.
One concerning example of what can go wrong is a flight from Greece to Wales on Aug. 25. The passengers included seven people believed to have been potentially infectious and 16 passengers later tested positive, the BBC reported. Travelers complained many people on board were ignoring basic precautions.
What studies have found:
Two studies that appear in the November edition of Emerging Infectious Diseases, a journal published by the CDC, suggest the new coronavirus virus can be transmitted during air travel.
But all of the research involves flights that took place several months ago when there were no measures in place to prevent transmission, like face masks or distancing passengers on the plane.
One study looked at a cluster of cases among passengers on a 10-hour flight from England to Vietnam on March 2.
Evidence "strongly" suggests one symptomatic passenger sitting in business class transmitted COVID-19 to at least 12 other passengers nearby — plus two travelers and one flight attendant in economy class — during the flight, the authors noted. Long flights can "provide conditions for superspreader events," they wrote, warning the risk for on-board transmission is "real," even with spacious seating arrangements in business class.
The other study found a cluster of four people with COVID-19, including two passengers and two members of the cabin crew, associated with a 15-hour flight from Boston to Hong Kong in early March. One or both of the passengers most likely contracted COVID-19 in North America and then transmitted the virus to the flight attendants, the authors wrote.
Previous research resulted in mixed findings.
A study published in August examined a flight from Israel to Germany in March. The passengers included 24 members of a tourist group who had recently had contact with a hotel manager who later tested positive for COVID-19.
When the plane arrived in Germany, seven of the 24 tourists tested positive for COVID-19. In addition, at least two other passengers later also tested positive — the authors noted they weren’t able to contact all 102 people on board plus the crew.
Both fliers with likely onboard transmission sat within two rows of the tourists who already had COVID-19, the study found.
Another analysis of an international flight, this one from China to Canada in January, found a sick passenger didn’t infect anyone else on board.
The odds of getting ill on a flight
Researchers said factors that may prevent transmission on planes include the airflow in the cabin from the ceiling to the floor, and all passengers wearing face coverings — a policy that’s now vigorously enforced by airlines. Most viruses don’t spread easily on flights because of how air circulates and is filtered on planes, the CDC noted.
Carriers like American Airlines have been touting the use of high-efficiency particulate air (HEPA) filters on board that capture “at least 99.97% of airborne microbes by circulating the cabin air once every 2 to 4 minutes.”
Policies that leave the middle seat open or otherwise limit the number of passengers on a plane are helping reduce the risk, too, Adalja said. Airlines have also implemented enhanced cleanings, temperature checks and traveler health acknowledgments during check-in.
A recent paper by Arnold Barnett, a statistics professor at the MIT Sloan School of Management in Cambridge, Massachusetts, looked at the probability of an air traveler contracting COVID-19 from a nearby passenger while sitting in economy class on a two-hour domestic U.S. flight. He assumed everyone was wearing masks.
Barnett calculated the risk at 1 in 4,300 for full flights, which went down to 1 in 7,700 when middle seats were kept empty.
It's not clear that two hours spent on a plane involved a higher COVID-19 infection risk than two hours doing any other everyday activities during the pandemic, Barnett concluded in the study.
"You don't get sick on airplanes any more than anywhere else," wrote Joseph Allen, an assistant professor of exposure assessment science at Harvard T.H. Chan School of Public Health in Boston, in The Washington Post. "The required aircraft systems do a really good job of controlling airborne bacteria and viruses."
Danger on the ground
Experts have been more worried about coronavirus spread before flights.
“My concern has really been in the airports funneling people through hallways and jet ways and metal detectors,” said Dr. Michael Mina, an epidemiologist at Harvard T. H. Chan School of Public Health, during a briefing in August. “The whole process of airports… and squishing people together. We know that this virus can be airborne and it can linger for a little bit.”
For that reason, Mina has chosen not to travel and hasn’t flown since February, he noted.
Any part of the trip where you can’t social distance is more risky since the virus transmits most efficiently when people are in close contact together, including at the airport food court and standing at the gate before boarding, Adalja added. He also believed people’s behavior at the destination is usually riskier than the journey itself.
If you plan to fly soon, Adalja recommended taking all the usual precautions during the trip: Wash your hands frequently, wear a face covering as required, avoid the crowded parts of the airport and try to stay 6 feet apart from everybody. Always have hand sanitizer with you.
Adalja is a major advocate of face shields, which he believes are superior to face masks because they’re easier to wear, protect your eyes and prevent you from touching your face. Given a choice, he’d wear a face shield on a plane, but noted some airlines may have rules specifically requiring a face mask.
Some studies have found the window seat may be best to avoid getting sick because it offers the least contact with other passengers, but Adalja was skeptical. It all depends on who's sitting beside you since it’s usually 10-15 minutes of close proximity — not fleeting contact — that transmits the new coronavirus virus, he said.
If you’re more likely to get the severe form of COVID-19, consider if it's worth the risk to fly. Don't fly if you're sick or have been in contact with someone who is sick. These are all important things to keep in mind as the holiday travel season approaches.
This article was updated in November 2020 to include the most recent research by United Airlines and the Department of Defense.