More than 1 million people traveled by plane in the US in one day, despite CDC COVID-19 guidelines

More than 1 million Americans are boarding planes despite warnings from the Centers for Disease Control and Prevention to avoid traveling for the Thanksgiving holiday.

On Friday, 1,019,836 passengers flew in the U.S., 1.5 million less than on the same day in 2019, according to daily figures from the Transportation Security Administration. The figure represents the second-highest number of people to travel by air since March. On Oct. 18, 1,031,505 people took to the skies.

Last week, the CDC cautioned against celebrating the upcoming holiday with people outside of the household, stating that the "safest way to celebrate Thanksgiving is to celebrate at home with the people you live with."

The extraordinary surge of a million new cases in the U.S. in the last 10 days has raised concerns that Thanksgiving gatherings could spread the virus further among families and communities, according to the agency.

"Travel may increase your chance of getting and spreading COVID-19. Postponing travel and staying home is the best way to protect yourself and others this year," the CDC guidelines state.

A Harvard review published last month found that wearing masks and the frequent cleaning in planes help keep the virus from spreading, and a study conducted by the Department of Defense and United Airlines also found that the risk of contracting COVID-19 on planes was 'very low' when proper measures are taken such as masks, frequent cabin cleaning, and distancing during boarding and deplaning help keep the virus from spreading.

However, the recent spike in positive cases has led several cities and states to mandate new COVID-19 restrictions ahead of the holiday season as hospital intensive care units begin to fill to capacity.

ABC News' Ahmad Hemingway contributed to this report.