The Federal Aviation Administration said flights departing for Los Angeles International Airport were halted Sunday morning due to a staffing shortage at a Southern California air traffic facility.

The FAA issued a temporary ground stop at one of the world’s busiest airports soon after U.S. Transportation Secretary Sean Duffy predicted that travelers would see more flights delayed and canceled in the coming days as the nation’s air traffic controllers work without pay during the federal government shutdown.

During an appearance on the Fox News program “Sunday Morning Futures,” Duffy said more controllers were calling in sick as money worries compound the stress of an already challenging job.

“Just yesterday, … we had 22 staffing triggers. That’s one of the highest that we have seen in the system since the shutdown began. And that’s a sign that the controllers are wearing thin,” he said.

The FAA said planes headed for Los Angeles were held at their originating airports starting at 11:42 a.m. Eastern time, causing delays averaging an hour and 40 minutes. The agency said it expected to lift the ground stop at 1:30 p.m. Eastern time but might continue to restrict traffic into LAX.

Staffing shortages also caused takeoff and arrival disruptions Sunday at New Jersey’s Newark Liberty International Airport and Teteboro Airport, and at Southwest Florida International Airport in Fort Meyers, Florida, according to the FAA.