Blocking middle seats on commercial jets does help reduce the spread of coronavirus.

That is according to a new US government report that follows several 2020 studies that showed the risk of transmission aboard jets is low.

The new analysis, conducted by the US Centers for Disease Control and Prevention (CDC) in partnership with Kansas State University, estimates that keeping middle seats empty could reduce the risk of coronavirus transmission 23-57%.

Southwest Airlines

Source: Southwest Airlines

Several US airlines had blocked middle seats in 2020, but most have reversed that policy. Delta Air Lines still keeps middle seats empty but will stop doing so after April.

“Research suggests that seating proximity on aircraft is associated with increased risk for infection with SARS-CoV-2, the virus that causes Covid-19,” says the report, released on 14 April.

In response to the findings, airline trade groups note the CDC’s analysis does not account for the use of face masks by passengers, which the CDC now requires.

Using a virus called “bacteriophage MS2” as a stand-in for airborne coronavirus, researches “modelled the relationship between… exposure and aircraft seating proximity”. The models examined exposure both on full flights and flights with middle seats empty.

“Compared with exposures in full occupancy scenarios, relative exposure in vacant middle seat scenarios was reduced by 23% to 57% depending upon the modelling approach,” the report says.

Those results led researches to conclude that “increasing physical distance between passengers and lowering passenger density could help reduce potential Covid-19 exposures during air travel”.

The study involved analysing data derived from a previous analysis virus-dispersal in cabin mock-ups, use of “regression modelling” to predict virus concentrations at distances from sources and simulations of how vacant seats affected exposure.

The CDC notes its review did not identically model conditions on aircraft. Data was collected at higher relative humidity levels than found on jets – humidity affects how quickly droplets evaporate – and the study did not account for face masks.

“Scientific studies that have taken into consideration mask-wearing have concluded that the risk of onboard transmission is very low,” trade group IATA tells FlightGlobal.

“Multiple scientific studies confirm that the layers of protection significantly reduce risk, and research continues to demonstrate that the risk of transmission onboard aircraft is very low,” says US trade group Airlines for America.

The airline industry has sought to assuage travelers’ safety concerns by pointing to other studies showing that the risk of virus transmission aboard aircraft is low.

Those include a US military study, released in October 2020, that concluded the “overall exposure risk from aerosolised pathogens, like coronavirus, is very low” aboard aircraft.

Also in October 2020, Harvard University released a report concluding that aircraft ventilation systems filter more than 99% of particles that cause Covid-19, which “effectively counters the proximity travellers are subject to”.

During a briefing that same month, IATA said only 44 cases of potential flight-related coronavirus transmission had been reported out of 1.2 billion travellers – and that was before widespread use of face masks.

Also, during that briefing, Airbus, Boeing and Embraer presented computational fluid dynamics research that, they said, showed cabin airflow systems limit virus spread.