(NewsNation) — Travelers celebrating Father’s Day and Juneteenth — a double holiday weekend — continue to face flight cancellations and delays for a fourth day in a row.

As of 1 p.m. ET on Sunday, airlines canceled 2,237 flights and delayed over 10,000 flights, according to tracking service FlightAware. Nearly 800 of Sunday’s cancellations and 2,000 of the delays involved aircraft scheduled to fly to or from U.S. cities.

Airports with the most cancellations Sunday included Atlanta’s International Airport, New York’s John F. Kennedy International Airport, Boston Logan International Airport, and Charlotte Douglas International Airport in North Carolina.

On Saturday, airlines canceled a total of 2,744 flights and delayed 18,171 flights. More than 800 canceled flights and 6,334 delayed flights were within, into, or out of the U.S., according to FlightAware.

On Friday, TSA officers screened 2.4 million people at airport security checkpoints nationwide, according to agency spokesperson Lisa Farbstein.

In a tweet, Farbstein said, “It was the highest checkpoint volume since Nov. 28, 2021, which was the Sunday after Thanksgiving.” Farbstein attributed the busy travel day to the start of the “Juneteenth Holiday Weekend.”

Transportation Secretary Pete Buttigieg met with airline leaders to quiz them about widespread flight disruptions after his own flight was canceled and he wound up driving from Washington to New York.

“That is happening to a lot of people, and that is exactly why we are paying close attention here to what can be done and how to make sure that the airlines are delivering,” Buttigieg told The Associated Press.

Buttigieg held a virtual meeting with airline CEOs to go over steps the airlines are taking to operate smoothly over the Fourth of July holiday and the rest of the summer and to improve accommodation of passengers who get stranded when flights are canceled.

Buttigieg said he is pushing the airlines to stress-test their summer schedules to ensure they can operate all their planned flights with the employees they have, and to add more customer service workers.

Buttigieg said his department could take enforcement actions against airlines that fail to live up to consumer protection standards. But first, he said, he wants to see whether there are major flight disruptions over the Fourth of July holiday weekend and the rest of the summer.

When the weekend’s cancellation problem started, the airlines blamed bad weather and the Federal Aviation Administration, an arm of the Transportation Department that manages the nation’s airspace, for the disruptions. Airlines have also acknowledged staffing shortages as travel roared back faster than expected from pandemic lows. Airlines are scrambling to hire pilots and other workers to replace employees whom they encouraged to quit after the pandemic hit.

So far in June, more than 2.2 million travelers a day on average have gone through security checkpoints at U.S. airports. That’s up 22% from a year ago although still down 13% from the same period before the pandemic.

The Associated Press contributed to this report.