As the summer air travel season continues, a concerning trend has developed with thousands of flights getting canceled this week. According to flight tracking website FlightAware, there were 1,759 “total cancellations within, into, or out of the United States” Thursday. Friday’s cancellation numbers topped 1,100 by early afternoon and were at 1,255 by mid-afternoon. Airports that have been most affected by the cancellations include:

• Charlotte Douglas International Airport
• LaGuardia Airport
• Newark Liberty International Airport
• Hartsfield-Jackson Atlanta International Airport
• Ronald Reagan Washington National  Airport
• John F. Kennedy International Airport
• Boston Logan International Airport

The concerning part of the recent cancellations is the fact that this weekend is not a particularly busy travel weekend. It’s sandwiched between Memorial Day Weekend and the 4th of July.

During Memorial Day weekend, which was expected to be one of the busiest for air travel since the pandemic began, airlines struggled with bad weather and shortages of workers. According to FlightAware, U.S. airlines canceled more than 2,800 flights from Thursday through Monday. That accounted for about 2% of airlines’ schedules.

With the 4th of July approaching, Transportation Secretary Pete Buttigieg held a virtual meeting with airline CEOs to go over steps the airlines are taking to make sure canceled flights don’t significantly hamper summer travel.

“I brought together airline leaders to focus on how they can ensure people get where they need to be, and back up their operations with responsive customer service,” Buttigieg tweeted Friday. “Air travelers should be able to expect reliable service as demand returns to levels not seen since before the pandemic.”

Delta Air Lines, which canceled the most flights over the Memorial Day weekend, said Friday it has reduced cancellations by hiring more pilots and flight attendants and by scheduling crews to adjust more quickly to disruptions such as thunderstorms. The airline’s comments came a day after its pilots published an open letter to customers describing the staffing shortages they have had to deal with.

“We have been working on our days off, flying a record amount of overtime to help you get to your destination,” the pilots wrote in the letter. “At the current rate, by this fall, our pilots will have flown more overtime in 2022 than in the entirety of 2018 and 2019 combined, our busiest years to date.”

The Associated Press contributed to this report.