Air travel chaos worsened with more than 4,300 flights delayed nationwide on Monday, following more than 8,800 delays on Sunday, with air traffic controller absences increasing as the federal government shutdown entered its 27th day.

According to the agency Reutersthe Federal Aviation Administration cited staffing shortages that affected flights throughout the Southeast and at its airport Newark at new jersey, while the agency imposed a landing ban at his airport Austin at Texas and International Airport landing delay schedule Dallas Fort Worth which delayed flights by an average of 18 minutes.

OR Southwest Airlines had 47% or 2,089 delays in its flights on Sunday, while American Airlines had 1,277 or 36% of its flight delays, according to FlightAware, a flight tracking website. OR United Airlines had 27% or 807 delays in its flights and Delta Air Lines had 21% or 725 flight delays.

About 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 air traffic controllers will not receive their first full paycheck on Tuesday.

On Monday, Southwest 24% of flights were delayed, American at 18% and Delta at 13% until 5:00 p.m. ET (2100 GMT), according to FlightAware.

A U.S. Department of Transportation official said 44 percent of Sunday’s delays were due to air traffic controller absences — up sharply from the usual 5 percent.

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

The Minister of Transport Sean Duffy found in Cleveland to meet with air traffic controllers on Monday, while the National Association of Air Traffic Controllers union plans rallies at several airports on Tuesday over the first missed pay.

The FAA has about 3,500 air traffic controllers who are understaffed and many were working mandatory overtime and working 6 days a week even before the government shutdown.

In 2019, during a 35-day lockdown, the number of screeners and TSA employee absences increased as workers did not receive their paychecks, resulting in longer wait times at some airport checkpoints. Authorities were forced to slow air traffic in New York and Washington.