You may be more likely to catch Covid-19 from someone at home than sitting on a packed, 12-hour flight with strangers.
That’s one takeaway from a new study on transmission of the virus on planes, sponsored by the Defense Department, in conjunction with
(ticker: BA), and
United Airlines Holdings
Airlines have tried for months to convince consumers that the risk of catching Covid on a flight is extremely low. And very few cases of in-flight transmission have been documented—just 44 this year, out of 1.2 billion passenger trips, according to the International Air Transport Association. (Some of those trips occurred before the pandemic.)
The study supports the notion that people aren’t likely to catch Covid on a plane, at least from the small aerosol droplets that face masks don’t filter out. Yet even if consumers buy in, the industry faces a long road to recovery.
Researchers simulated virus-particle transmissions on Boeing 777 and 767 wide-body planes over eight days of testing, both in flight and on the ground. The planes were equipped with High Efficiency Particulate Air (HEPA) filters, which are now commonly used on commercial flights. Researchers conducted more than 300 aerosol tests, releasing 180 million “fluorescent tracer particles” into the air, and used sensors and mannequins to estimate exposure and transmission without using the actual virus.
The results were encouraging. HEPA filters, high rates of air exchange, and downward ventilation systems all combined to scrub the virus particles almost entirely out of cabin air. Researchers found a 99.7% reduction in particles circulated to passengers seated directly next to the source of transmission, and a 99.9% reduction in more than 40 “breathing zones” in each section of the aircraft.
Catching Covid would be “extremely unlikely” on a 12-hour flight, the researchers concluded. Indeed, a passenger in economy class would need to sit next to a contagious passenger for 54 straight hours to be infected, according to theoretical models. And it would take more than 100 hours of flight time for passengers elsewhere on the plane to be infected.
As one might expect, transmission risk was highest in the same row as a contagious passenger, along with the rows in front and behind. But there was no measurable difference between window, middle, or aisle seats. Overhead air vents, on or off, didn’t make a difference.
Researchers also studied the jetway with the aircraft door open, checking to see if the virus was transmitted from a mannequin in row 33. They found that 99.99% of virus particles were eliminated in that scenario.
The study implies that a packed flight would actually be safer than staying home with a contagious person. Aerosol droplets on a plane decay or disperse in about five minutes, versus 1.5 hours in a suburban house, the study found. And because time of exposure is critical, the cumulative exposure on a plane was 10 times less because of the rapid air recirculation, filtration and