The FAA said many flights were being delayed at Nashville and Newark airports, among others. Arriving flights were being held for up to 30 minutes at Newark due to the staffing issues.

Nashville air traffic control is facing significant staffing issues and will curtail operations later on Tuesday, the FAA said. Approach control will be taken over later by Memphis Center, it added.

The FAA is reducing the number of arriving flights per hour at Chicago O’Hare, citing staffing, with average delays of 41 minutes.

The FAA also reported staffing issues at Atlanta Air Route Traffic Control Center.

Severe weather is also impacting flights across the country.

Some 13,000 air traffic controllers and about 50,000 Transportation Security Administration officers must still turn up for work during the government shutdown, but they are not being paid. Controllers are set to receive a partial paycheck on Oct 14 for work performed before the shutdown.

Transportation secretary Sean Duffy said on Monday the FAA had seen a slight increase in controllers taking sick leave and air traffic staffing has been cut by 50% in some areas since the shutdown started last week.

“If we don’t have controllers, we’re going to make sure the airspace is safe. So what we do is we’ll slow traffic,” Duffy said on Tuesday on Fox News’ “Fox and Friends.”

FlightAware, a flight tracking website, said more than 2,500 flights had been delayed on Tuesday, including about 200 at Nashville, or 20% of its flights, and nearly 500 flights at Chicago O’Hare, or more than 15% of flights.

In 2019, during a 35-day shutdown, the number of absences by controllers and TSA officers rose as workers missed paychecks, extending checkpoint wait times at some airports. Authorities were forced to slow air traffic in New York, which put pressure on lawmakers to quickly end the standoff.