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 downward ventilation.
The research had a few limits. The mannequins were kept seated, facing forward. Researchers didn’t evaluate movement in the plane, jetway, or airport lounges. They also didn’t assess the impact of conversation, which could change the direction of particles. They assumed that passengers wore masks the entire time. And they only focused on the smallest, aerosol droplets, assuming masks would filter out larger droplets resulting from talking, coughing, or sneezing. Virus particles could also land on surfaces and infect people.
Still, even if airlines succeed in convincing the public that flying is safe, the industry faces broader obstacles to a recovery. A second wave of cases is building in the U.S. and Europe, approaching the summer peaks, and countries such as France are reimposing some lockdown measures. Carriers don’t expect a big rebound in air traffic without a vaccine and overall easing of the pandemic.
The full-service network carriers, such as United, are likely to face the longest recovery, since their networks and route structures rely more heavily on international and business fares (compared to leisure-focused domestic carriers). United, for instance, says it expects fourth-quarter revenue to be down 67%, compared to 2019 levels, with capacity down 55%. That implies capacity in the first quarter of 2021 would be at least 50% below 2019 levels, according to UBS analyst Myles Walton.
United’s guidance, he wrote, was “further confirmation of the lack of coiled spring recovery on 2021, and the need for material consensus negative revisions to earnings/cash (on all US airlines).”
Without much sign of demand rebounding, Walton maintained a Neutral rating on the stock. He cut his target for the stock price to $33 from $36.
Write to Daren Fonda at [email protected]