(NewsNation) — U.S. Transportation Secretary Sean Duffy on Thursday ordered scheduled air traffic cut by 10% at 40 major airports starting Friday without a deal to end the government shutdown.

The shutdown has forced 13,000 air traffic controllers and 50,000 Transportation Security Administration officers to work without pay and snarled tens of thousands of flights.

Duffy had warned on Tuesday that if the federal government shutdown continues another week it could lead to "mass chaos" and could force him to close some of the national airspace to air traffic, a drastic move that could upend American aviation.

Airlines have repeatedly urged an end to the shutdown, citing aviation safety risks.

There have already been numerous delays at airports across the country — sometimes hours long —

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