The Transportation Security Administration screened 616,469 people at airport security checkpoints across the United States on Christmas Day, the agency said Saturday.

That's just 23 per cent of the number of travellers who flew the same day a year ago, before the pandemic, and about half of the 1.2 million passengers who flew on Wednesday, setting a pandemic air travel record. On Thursday, Christmas Eve, 846,520 people passed through TSA checkpoints.

Smaller passenger numbers on Christmas Eve and Christmas Day mark a lull before numbers begin to tick up again, as people head home from holiday travels.

Sunday is expected to be another big day for air travel, travel experts say. TSA numbers show that in the last week, nearly 7 million people were screened at airport security checkpoints.

The holiday travel rush comes even after the U.S. Centers for Disease Control and Prevention urged Americans to stay home to avoid spreading coronavirus. The increase in air travel is stoking new fears among health experts of another jump in COVID-19 infections, similar to a spike recorded following the previous pandemic air travel record set around Thanksgiving.

"We need to try to bend the curve, stop this exponential increase and so we're really asking the American public to prevent these infections and avoid travel and wash their hands, wear a mask and maintain distance," Dr. Henry Walke, the CDC's COVID-19 incident manager, said earlier this month.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told CBS earlier this month that he would not spend the Christmas holiday with his daughters for the first time in more than 30 years.

The uptick in travel also comes as executives from several airlines look to bring back thousands of workers who were furloughed in the fall because of depressed travel numbers.

Congress' latest COVID-19 relief bill includes an extension of the airline industry's Payroll Support Program, which sets aside US$15 billion in assistance to rehire more than 32,000 United and American Airlines employees furloughed in September. The companies say the additional funds are enough to pay those workers through March 31.

--CNN's Chauncey Alcorn contributed to this report.