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.
Unions say many employees are becoming ill with stress or are being forced into taking second jobs.