National Institute of Allergy and Infectious Diseases director Dr. Anthony Fauci said that taking masks off while on an airplane is "not something we should even be considering."

Fauci made the comments while on ABC's This Week on Sunday and was responding to a question from Jonathan Karl on a vaccine mandate for domestic air travel.

"We want to make sure people keep their masks on. I think the idea of taking masks off, in my mind, is really not something we should even be considering," Fauci said. 

"And of course, the airline CEOs were suggesting that -- you know, that we may not -- may no longer need a mask. I hear you loud and clearly, you disagree with that on an -- on the airplane," Karl responded.

FAUCI SAYS MASKS ON PLANES WILL ALWAYS BE NECESSARY NO MATTER WHAT: 'GO THAT EXTRA STEP'

Dr. Anthony Fauci

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks during the daily briefing at the White House in Washington, Wednesday, Dec. 1, 2021. (AP)

During a U.S. Senate panel hearing on Dec. 15, Southwest Airlines CEO Gary Kelly said that masks "don’t add much, if anything" to fight the spread of COVID-19 on airplanes.

When answering the question, Fauci also signaled that a vaccine mandate for domestic air travel could work as a mechanism for individuals to get vaccinated.

"A vaccine requirement for a person getting on the plane is just another level of getting people to have a mechanism that would spur them to get vaccinated; namely, you can't get on a plane unless you're vaccinated, which is just another one of the ways of getting requirements, whatever that might be," Fauci said.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks during the daily briefing at the White House in Washington, Wednesday, Dec. 1, 2021, as White House press secretary Jen Psaki watches.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks during the daily briefing at the White House in Washington, Wednesday, Dec. 1, 2021, as White House press secretary Jen Psaki watches. (AP Photo/Susan Walsh)  (AP)

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"So I mean, anything that could get people more vaccinated would be welcome. But with regard to the spread of virus in the country, I mean, I think if you look at wearing a mask and the filtration on planes, things are reasonably safe," he added.

During the Dec. 19 "This Week" episode, Fauci said that he doesn't think there will be a point where masks are unnecessary on airplanes.

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Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks during a Senate Health, Education, Labor, and Pensions Committee hearing on Capitol Hill, Thursday, Nov. 4, 2021, in Washington.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks during a Senate Health, Education, Labor, and Pensions Committee hearing on Capitol Hill, Thursday, Nov. 4, 2021, in Washington.  (AP Photo/Alex Brandon)

"I think when you're dealing with a closed space, even though the filtration is good that you want to go that extra step," Fauci said. "When you have people, you know you get a flight from Washington to San Francisco, it's a well over a five-hour flight."

"Even though you have a good filtration system, I still believe that masks are a prudent thing to do and we should be doing it," he added. 

Fox News' Peter Aitken contributed to this report