LOS ANGELES (CBSLA) – Commercial airlines which leave their middle seats empty on flights can greatly reduce the transmission of COVID-19, according to a new study published Wednesday by the Centers for Disease Control and Prevention.

The study, conducted by the CDC and Kansas State University, found that the spread of COVID-19 was reduced by anywhere from 23% to 57% — depending on the modeling and the type of cabin arrangement — when airlines left the middle seat vacant, compared to when they operated at full capacity.

FILE — Tom Bradley International Terminal at Los Angeles International Airport on Feb. 4, 2021. (Getty Images)

At the beginning of the pandemic, several U.S. airlines undertook the practice of blocking middle seats. However, Delta is the only one still doing so, and it will end the policy on April 30.

The researchers conducted lab experiments using bacteriophage aerosols as a substitute for pathogenic viruses such as COVID-19. The aerosols were dispersed in an aircraft cabin mock-up with mannequins as passengers.

The results suggested that “increasing physical distance between passengers and lowering passenger density could help reduce potential COVID-19 exposures during air travel,” the study authors determined. “Physical distancing of airplane passengers, including through policies such as middle seat vacancy, could provide additional reductions in SARS-CoV-2 exposure risk.”

The study did not take masks into consideration, which are required on all flights. It’s unclear if the findings will affect the CDC’s travel guidelines.

“The flight was pretty crowded, but still, I feel pretty confident with everybody being vaccinated,” passenger Christopher Martinez told CBSLA Wednesday after disembarking a flight at the Burbank Airport.

Passenger Dave True said there’s a risk of exposure regardless of how careful you are.

“Before boarding the plane everybody’s standing this close together,” True said. “And as we’re all walking on everyone’s this close together, so does it matter if you catch it in this five minutes or the next five minutes?”

Currently, all domestic passengers are advised to undergo a COVID-19 test both before and after travel unless they have been fully vaccinated. Last week, Los Angeles County health officials updated the county’s travel advisory to say that people who are fully vaccinated can travel without testing or quarantining.

All international travelers coming to the U.S. are required to show proof of a negative coronavirus test no more than three days prior to boarding their aircraft, regardless of whether or not they have been fully vaccinated.