US Transportation Secretary Sean Duffy has warned that air travel capacity will be cut by up to 10% at 40 major airports over the coming days, if the government shutdown continues.
The decision, which is expected to affect domestic flights only, was made because air traffic controllers had been reporting fatigue, the head of the Federal Aviation Administration (FAA) said at a briefing alongside Duffy.
Some 1.4 million federal workers, from air traffic controllers to park wardens, are working without pay - or are on forced leave - because the US Congress has not agreed a federal funding budget.
On Wednesday, the impasse became the longest shutdown in US history. The flight reductions will be gradual, starting at 4% of domestic flights on Friday, then rising to 5% on Saturday and 6% on Sunday, before hitting the full 10% next week, the Reuters news agency reported, citing four unnamed sources.
The names of the affected airports - all high-traffic locations - would be released on Thursday, the officials said. US media including the BBC's partner CBS News reported that the list would include some of the nation's busiest hubs, including Hartsfield-Jackson Atlanta International, Dallas/Fort Worth International, Denver International, Chicago O'Hare International, and Los Angeles International.
The cancellations could affect between 3,500 and 4,000 flights per day. US media also reported that international flights would not be affected.
Duffy insisted that air travel was still safe, and the decision to cancel the flights was being made to maintain safety and efficiency.
In a statement, American Airlines, the second-largest carrier in North America, said it expected the vast majority of its customers' travel would be unaffected. A spokesperson for Southwest Airlines stated they were still evaluating how the flight restrictions would affect their services.
Nick Daniels, the president of the labor union representing more than 20,000 aviation workers, depicted stark realities, emphasizing that air traffic controllers feel stressed and financially strained as they juggle work without pay.
As the government shutdown drags on, the aviation sector is bracing for potentially significant disruptions, with officials warning that further measures might be needed if conditions worsen.