Dr. Anthony Fauci, President Biden’s chief science adviser on the COVID-19 response, said in an interview Monday that the U.S. should consider a vaccine requirement for domestic air travel.

Fauci told MSNBC that vaccine requirements are added incentive for people to roll their sleeves up for the jab.

Dr. Anthony Fauci, the top U.S. infectious disease expert, wears a face mask during the White House COVID-19 Response Team's regular call with the National Governors Association in the South Court Auditorium in the Eisenhower Executive Office Building on the White House Campus. (AP Photo/Carolyn Kaster)

"If you want to do that with domestic flights, I think that’s something that seriously should be considered," he said.

The Associated Press pointed out that the Biden administration has balked at imposing such a mandate. Fauci’s National Institute of Allergy and Infectious Diseases did not immediately respond to an after-hours email from Fox News.

About 77% of eligible Americans have taken at least one jab.

Fauci told ABC’ "This Week" on Sunday that taking masks off while on an airplane should not even be considered. His comment came after Southwest Airlines CEO Gary Kelly told a U.S. Senate panel Wednesday that "masks don't add much, if anything" in fighting the spread of COVID-19 on airplanes.

Kelly said, "The statistics I recall is that 99.97% of airborne pathogens are captured by the [high-efficiency particulate air] filtering system, and it's turned over every two or three minutes."

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"I think the case is very strong that masks don't add much, if anything, in the air cabin environment," Kelly said. "It's very safe, and very high quality compared to any other indoor setting."

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Two officials told the AP that Biden’s science advisers have yet to make a formal recommendation for such a requirement to the president.

Fox News' Adam Sabes, Breck Dumas and the Associated Press contributed to this report