President Joe Biden's medical adviser said a domestic travel vaccination rule should be considered as the omicron variant fuels record COVID-19 case loads in some states and holiday travel continues to be disrupted around the U.S. 

Anthony Fauci said on MSNBC on Monday that it would be "reasonable to consider" a requirement to be vaccinated for the coronavirus before getting on a domestic flight. Later, in an interview on CNN, he said people should consider avoiding larger New Year's Eve parties.

"When you make vaccination a requirement, that's another incentive to get more people vaccinated," Fauci said. "If you want to do that with domestic flights, I think that's something that seriously should be considered."

A surge in cases prompted U.S. airlines to scrap about 2,800 flights over the holiday weekend because of personnel shortages, and has disrupted plans for some of the traditional year-end college football games.

While some studies have suggested the omicron variant is less severe, particularly for vaccinated people, rising case loads have prompted concerns that hospitals could still be overwhelmed with patients, a situation now being seen in pockets of the U.S.