WASHINGTON — Air travel turmoil deepened with more than 2,700 flights delayed nationwide on Monday and more than 8,600 delays on Sunday, with air traffic controller absences surging amid a federal government shutdown now in its 27th day.

The Federal Aviation Administration cited staffing shortages affecting flights across the Southeast and at Newark Airport in New Jersey, while the FAA imposed a ground delay at Los Angeles International that delayed flights by an average of 25 minutes.

Southwest Airlines had 45%, or 2,000, of its flights delayed on Sunday, while American Airlines had nearly 1,200, or a third, of its flights delayed, according to FlightAware, a flight-tracking website. United Airlines had 24%, or 739, of its flights delayed and Delta Air Lines had 17%, or 610, of its flights delayed.

Roughly 13,000 air traffic controllers and 50,000 Transportation Security Administration officers must work without pay. The Trump administration has warned that flight disruptions will increase as controllers miss their first full paycheck on Tuesday.

On Monday, Southwest had 15% of flights delayed, American 12% and Delta 9% as of 1:30 p.m. EDT (1730 GMT), according to FlightAware.

A U.S. Department of Transportation official said 44% of Sunday’s delays stemmed from controller absences — up sharply from the usual 5%.

The mounting delays and cancellations are fueling public frustration and intensifying scrutiny of the shutdown’s impact, raising pressure on lawmakers to resolve the budget impasse.

The FAA is about 3,500 air traffic controllers short of targeted staffing levels and many had been working mandatory overtime and six-day weeks even before the shutdown.

In 2019, during a 35-day shutdown, the number of absences by controllers and TSA officers rose as workers missed paychecks, extending wait times at some airport checkpoints. Authorities were forced to slow air traffic in New York and Washington.

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(Reporting by David Shepardson; Editing by Howard Goller)