SEATAC, WA - NOVEMBER 29: Travelers pass through security screening at Seattle-Tacoma International Airport on November 29, 2020 in SeaTac, Washington. Public health experts warn that COVID-19 cases may surge following holiday travel, as the U.S. surpasses 4 million cases so far this month. (Photo by David Ryder/Getty Images)
CNN  — 

While Thanksgiving travel has certainly been far lighter than usual, US air travel hit its highest level since mid-March over the holiday and millions of Americans still traveled by car to join family and friends.

More people passed through US airport security checkpoints on Sunday than on any other single day since the coronavirus pandemic cratered air travel, according to the Transportation Security Administration.

TSA said it screened 1.17 million people on Sunday when many Americans were heading home from their Thanksgiving travels. That was 41% of the 2.9 million people screened by TSA on the same day in 2019. Thanksgiving 2019 set a TSA record.

That means more than 9.4 million people have been screened in the Thanksgiving travel window, which began on the Friday before the holiday.

Since the pandemic gutted air travel in mid-March, checkpoints have screened more than one million passengers on only five days. Four occurred over the Thanksgiving holiday period.

Travel raises fears of Covid-19 transmission

The Centers for Disease Control and Prevention advised against Thanksgiving travel, fearing families mingling would spread the virus.

Public health officials this weekend recommended those who did travel for Thanksgiving should quarantine themselves and get tested for the coronavirus as cases surge nationwide.

White House coronavirus coordinator Dr. Deborah Birx said Sunday she is “deeply worried” Thanksgiving travel will cause another virus spike.

“We know people may have made mistakes … over the Thanksgiving time period,” she said in a Sunday interview on CBS. “If your family traveled, you have to assume that you are exposed and you became infected and you really need to get tested in the next week.”

Airlines have argued travel on an airplane is very safe – safer than being in many other public spaces – because of hospital-grade air filtration and ventilation that regularly replaces air in the cabin.

But there has been less study about other parts of the air travel experience – including crowded airport lines and shuttle buses.

And then there’s the risk of spread when travelers arrive at their destination.

Car trips down significantly

A week before the holiday period kicked off, travel organization AAA projected at least a 10% drop in overall travel during the holiday time frame, which the organization defined as the Wednesday before Thanksgiving to the Sunday after.

Of those expected to travel, AAA predicted 95% – nearly 48 million Americans – would travel by car.

With the CDC guidance against traveling issued just before Americans set off and the continued spike in Covid-19 cases, AAA spokeswoman Julie Hall said on November 19 that “AAA expects the actual number of holiday travelers will be lower than forecasted.”

AAA won’t have actual figures for some time, Hall said.

Yet data from Arrivalist, which tracks GPS signals representing consumer road trips of 50 miles or more in the US, indicates a 35% drop in Thanksgiving road trips from last year.

Those results mark a departure from earlier holidays in 2020, such as the Fourth of July and Labor Day, when road trips were close to or exceeded 2019 levels.

Arrivalist’s Daily Travel Index data on road trips indicates that Thanksgiving has been the least traveled major holiday of the year so far, with less road-trip activity than Memorial Day.

The data was compiled from trips initiated on Wednesday, November 25 or Thursday, November 26, compared to the same days of the holiday week last year.

“Travel by private car – generally regarded as one of the safest and most available means of leisure travel during the pandemic – had begun establishing itself as a leading indicator of travel’s rebound,” said Arrivalist CEO, Cree Lawson, in a statement.

“That appears to have taken a back seat to people’s desire to protect themselves and each other from a surge of Covid-19 cases.”

CNN’s Chris Isidore contributed to this report.