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.
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.
"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.
"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