WASHINGTON (AP) — Air traffic in the U.S. could “slow to a trickle” if the federal government shutdown lingers into the busy Thanksgiving travel holiday season, Transportation Secretary Sean Duffy warned Sunday.

The Federal Aviation Administration (FAA) has ordered flight reductions at the nation’s busiest airports due to escalating staffing shortages. Air traffic controllers, many of whom have been unpaid, are increasingly absent from work, leading to significant disruption.

Current reductions began at 4% and are projected to rise to 10% by Nov. 14, affecting commercial flights from 6 a.m. to 10 p.m. local times.

By 1:30 p.m. Eastern time on Sunday, more than 1,700 flights were canceled and nearly 5,000 flights were delayed due to ongoing issues, including major disruptions at Hartsfield-Jackson and Newark Liberty airports.

With a predicted increase in flights during the Thanksgiving holiday, Duffy emphasizes that travelers will face massive disruption if current trends continue. He expressed concerns about air traffic controllers continuing to retire amid the shutdown.

Despite suggestions of utilizing military air traffic controllers, Duffy clarified that any such help would require proper certification to work on civilian systems. The ongoing political climate surrounding the shutdown has further complicated the response to the growing crisis.

As millions prepare to travel for the holiday, both airline and FAA officials are bracing for a chaotic travel season, with potential staffing levels significantly below necessary thresholds.