Air passengers across the United States faced extensive flight cancellations and delays this weekend, caused by a boom in travel demand coupled with widespread staffing shortages.

From Friday through Sunday, airlines that fly within, into, or out of the United States canceled more than 1,400 flights, according to FlightAware, a flight-tracking website, stranding and angering some passengers headed for long-awaited summer vacations. In addition, more than 14,000 flights were delayed this holiday weekend, according to the site’s data.

Some airlines seemed to be struggling to handle passenger volume that approached or in some cases even exceeded prepandemic levels. On Friday, the Transportation Safety Administration screened more passengers — 2.49 million people — than on any other day this year. That surpassed the 2.18 travelers screened on July 1, 2019, before the pandemic.

The experience was frustrating for some passengers on U.S. carriers. On Saturday, 1,048 — or 29 percent — of Southwest Airlines flights were delayed, as were 28 percent of American Airlines flights, according to FlightAware. United Airlines and Delta Air Lines had similar problems, with 21 percent and 19 percent of their flights also delayed. On Sunday, the middle of the holiday weekend, travelers seemed to be getting a respite from the worst of the problems.

“Obviously, if it’s your flight that is delayed or canceled, it’s a disaster,” said Robert W. Mann Jr., a former airline executive who now runs the airline consultancy R.W. Mann & Company.

In a typical month, Mr. Mann noted, about 20 percent of flights are delayed or canceled. But this holiday weekend, he said, about 30 percent of flights were delayed or canceled — a 50 percent increase. “It’s a little bit worse than usual,” he said.

Adding to the pressure on air carriers this weekend was a glitch in the pilot-scheduling system at American Airlines that enabled pilots to drop thousands of flight assignments for July. The airline said on Saturday that it did not anticipate any “operational impact” because of the glitch.

But the Allied Pilots Association, the union for American Airlines pilots, said that the airline had unilaterally reinstated the dropped trips without the agreement of the pilots. The union said it was pressing the airline to pay an “inconvenience premium” to pilots affected by the scheduling system problems.

In a nod to mounting passenger frustrations this summer, Ed Bastian, the chief executive of Delta Air Lines, issued an apology last week.

“I know many of you may have experienced disruptions, sometimes significant, in your travels as we build our operation back from the depths of 2020 while accommodating a record level of demand,” Mr. Bastian wrote in a post on LinkedIn. He added: “Though the majority of our flights continue to operate on time, this level of disruption and uncertainty is unacceptable.”

In an email, Morgan Durrant, a spokesman for Delta, said the airline was managing “the compounding factors” of bad weather and air traffic control delays, which affect the availability of flight crews. The airline was “working around the clock to make Delta’s operation as resilient as possible to minimize the ripple effect of disruptions,” Mr. Durrant said. “Even so, some operational challenges are expected this holiday weekend.”

As the holiday weekend progressed, however, the spate of flight problems began to abate. By Sunday evening, Delta had canceled just 1 percent of its flights, and just 15 percent of Southwest Airlines flights had been delayed, according to FlightAware.

Southwest said on Sunday that it was delivering “a safe, reliable experience across our network today with currently, less than 10 total cancellations” for the day.

American Airlines and United Airlines did not immediately respond to emails seeking comment.

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