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 last week ordered flight cuts at the nation’s busiest airports as some air traffic controllers, who have gone unpaid for nearly a month, have stopped showing up for work.

The reductions started Friday at 4% and will increase to 10% by Nov. 14. They are in effect from 6 a.m. to 10 p.m. local time and will impact all commercial airlines.

On Sunday, 1,375 flights were canceled as of 10:30 a.m. Eastern time, according to the aviation tracking website FlightAware. That follows more than 1,500 cancellations on Saturday.

Duffy has said additional flight cuts — perhap

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