Research by Harvard’s TH Chan School of Public Health found layering a range of "risk mitigation strategies", such as the universal wearing of face masks, introduction of stringent new cleaning and disinfection protocols, and insistence on advanced air ventilation and filtration systems, significantly lowered the risk of Covid transmission onboard aircraft.

The "gate-to-gate" study concluded the risk of Covid transmission in-flight is below many "routine activities" that have continued during the pandemic.

"Implementing layered risk mitigation strategies... will help ensure air travel, with respect to SARS-CoV-2 [Covid-19] transmission, is as safe or substantially safer than the routine activities people undertake during these times," read the Harvard report.

"This layered approach, with ventilation gate-to-gate, reduces the risk of transmission onboard aircraft [to] below that of other routine activities during the pandemic, such as grocery shopping or eating out."

Specifically on face masks, the report added: "Face mask requirements are perhaps the most essential layer of a comprehensive set of measures to reduce transmission of Covid-19 throughout air travel."

Echoing recent Iata research, the Harvard team found there has been "little evidence" of onboard transmission of Covid-19 since the wearing of face masks and enhanced cleaning routines onboard aircraft became commonplace in the spring.

"Case studies that do find such transmission report data prior to implementation of strict face mask policies," said the Harvard report.

"While investigation of the virus and its transmission is ongoing, the research to date indicates a relatively very low risk of acquiring SARS-CoV-2 while flying."

Other measures that have contributed to the negligible transmission of Covid during flights include social distancing throughout the airport journey, while boarding, during the flight, and when disembarking.

The report also recommends airlines strictly enforce boarding and disembarking in a "managed, orderly and distanced" row-by-row sequence to avoid people standing up as soon as the aircraft lands and then "loitering" in the aisle.