The government shutdown is now rippling through airports across the country.
Flights at several major airports were delayed Monday because of air traffic controller staffing shortages.
Air traffic controllers and TSA employees are considered essential workers, so they're working without pay.
But Transportation Secretary Sean Duffy says there's been an uptick in the number of air traffic controllers calling in sick.
"If we have additional sick calls, we will reduce the flow consistent with a rate that's safe for the American people," Duffy said.
Duffy acknowledged the shutdown makes an already stressful job more challenging.
"They're not just now thinking about the airspace and the jobs they have to do in these towers or TRACONS or centers across the country, they're thinking about, 'am I going to get a paycheck?'" Duffy said. "In a job that's already stressful, this shutdown has put way more stress on our controllers."
On Monday, more than 6,000 U.S. flights were delayed, according to FlightAware.
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As of midday Tuesday, more than 1,400 U.S. flights were delayed.
Delays could worsen if the shutdown drags on — with the U.S. already experiencing a shortage of air traffic controllers ahead of the government work stoppage.
The union representing those workers is calling on lawmakers to end the shutdown immediately.
"We do not have time to waste on the unnecessary distractions created by this shutdown," said Nick Daniels, president of the National Air Traffic Controllers Association. "So our message is clear. End the shutdown."
