The latest on the coronavirus pandemic: Live updates – cnn.com

A sign reminds travelers to wear face coverings displayed at an American Airlines Group Inc. boarding gate at Los Angeles International Airport in Los Angeles, California, U.S., on Thursday, Oct. 1, 2020. 
A sign reminds travelers to wear face coverings displayed at an American Airlines Group Inc. boarding gate at Los Angeles International Airport in Los Angeles, California, U.S., on Thursday, Oct. 1, 2020.  Patrick T. Fallon/Bloomberg/Getty Images

Experts are giving mixed messages about the Covid-19 risks of air travel as Americans consider their Thanksgiving holiday plans.  

A Harvard University study released Tuesday modeled the airflow in airliners and say the specialized onboard ventilation systems filter out 99% of airborne viruses. 

The team of scientists concluded that a “layered approach, with ventilation gate-to-gate, reduces the risk of SARS-CoV-2 transmission onboard aircraft below that of other routine activities during the pandemic, such as grocery shopping or eating out.”  

A contract tracing study released by Irish researchers linked 13 cases to a single passenger on a seven-hour international flight this summer where fewer than one in five seats were filled. Some passengers may not have been wearing masks.

The researchers conclude that some of the spread must have occurred on the plane because some of the passengers “had no social or airport lounge link with Groups 1 or 2 pre-flight and were not seated within two rows of them.” 

The Harvard researchers described wearing masks as a critical part of keeping travelers safe in aircraft cabins, but stopped short of calling for a government mask mandate onboard flights. But with people bunching up in jetways, aisles, and airports – where ventilation systems may not be as efficient as those on aircraft, they say more research needs to be done.

The Harvard findings mirror those from recent studies from The Department of Defense, Boeing, and Airbus as airlines are struggle to bring domestic passenger traffic above 40 percent of last year’s levels.

Last week, Southwest Airlines cited the earlier studies as the reason to resume the sale of every seat on its flights starting December 1.