Today is expected to be one of the busiest travel days of the pandemic as hundreds of thousands of Americans return from Christmas celebrations.

As of Sunday morning, the arrival area inside Terminal B at LaGuardia airport was quiet.

Air travel this year has been way down compared to pre-pandemic levels. But despite warnings from medical experts to stay home, travel surged over the Christmas holiday to a level not seen since March.

The TSA reports that a record 1.1 million Americans boarded airplanes two days before Christmas -- the most travelers since before the pandemic began. Four point six million people traveled over four days leading up to Christmas Day. 

These numbers suggest that Americans are not heeding CDC’s guidance to not travel unless absolutely necessary. 

A TSA spokesperson tweeted that the days after Christmas are usually very busy travel days, and advised those returning home to mask up. 

"Christmas day isn't typically a very busy day for air travel, however the day or two afterward are usually busier as people head home after the holiday. If you choose to travel, please mask-up," she wrote in the tweet.

In response to the new strain of the coronavirus, testing requirements go into effect for travelers coming to America from the UK beginning Monday. 

Airlines must confirm a negative test for travelers. If a passenger chooses not to take a test, the airline is required to deny boarding.

The new strain of COVID-19 has also been detected in Japan, France, Spain, Sweden and Canada, regions that are not subjected to the same testing requirements.

Appearing on CNN’s "State of the Union" Sunday, Dr. Anthony Fauci addressed whether the imposition of testing on travelers from the UK is happening too late.

“I’m not going to say it was a mistake or not,” Fauci said. “I think it’s prudent and a good idea to do some form of testing and not let somebody on the plane from the UK, unless they have a documented negative COVID-19 test. So I agree with that. I mean, you could argue about the timing, whether it should’ve been done a few days before.”