Transport Minister Sean Duffy warned that air travel capacity at 40 major US airports would be cut by 10% from Friday if the government shutdown continues.
The decision comes because air traffic controllers are reporting problems with fatigue, the head of the Federal Aviation Administration (FAA) said in a briefing with Duffy.
“This is unusual, just as the outage is unusual, it is also unusual that our dispatchers have not been paid for a month,” said FAA Commissioner Brian Bedford.
About 1.4 million federal workers, from air traffic controllers to park rangers, are working without pay or on furlough because Congress has failed to agree on a federal funding budget.
Unions say many employees are falling ill due to stress or are being forced to look for second jobs due to financial pressure from the longest lockdown in U.S. history.
The flight cuts will be gradual, starting with 4% of domestic flights on Friday, then increasing to 5% on Saturday and 6% on Sunday before reaching the full 10% next week, Reuters reported after the announcement, citing four unnamed sources.
The names of the affected airports – all high traffic areas – will be released on Thursday, officials said.
The cancellation could affect between 3,500 and 4,000 flights per day.
“We're seeing the pressure build in a way that we believe – if we allow this to go unchecked – it will prevent us from continuing to tell the public that we run the safest airline system in the world,” Bedford said.
Duffy said air travel remains safe and the decision to cancel flights was made to ensure safety and efficiency.
If the shutdown continues and puts additional strain on the system, additional restrictive measures may be needed, Bedford said.
In a statement, American Airlines, North America's second-largest carrier, said it was awaiting more information from the FAA to determine which flights would be cancelled, but “we expect the vast majority of our customers' travel will not be affected.”
A spokesman for Southwest Airlines, the fourth-largest airline, said in a statement that the company was still assessing how the flight restrictions would impact its service and would let customers know as soon as possible.
“We continue to urge Congress to immediately end the impasse and restore the National Airspace System to full capacity,” the spokesperson added.
Delta Airlines declined to comment. The BBC has also contacted other major US airlines.
When government funds ran out on Oct. 1, most federal workers were sent home and told they would be paid as soon as the government reopened. However, those deemed essential, such as supervisors, had to continue to do their jobs without pay.
Almost immediately after the closure began, airports began to feel the effects. Some had to ground flights for several hours after air traffic controllers called in sick, while others relied on controllers at other airports.
Nick Daniels, president of the union representing more than 20,000 aviation workers, described the situation in harsh terms Wednesday.
“Air traffic controllers write, 'I don't even have money to put gas in my car to come to work,'” he told CNN.
“We base what we do day-to-day on predictability,” he said. “There is no predictability right now.”
Earlier this week Duffy warned that flight cancellations may occuras half of the country's 30 largest airports face staff shortages.
He previously said there was a risk of air traffic controllers taking on extra work during the shutdown and threatened to fire controllers who don't show up for work.
“They have to make a decision, am I going to go to work and not get paid and not put food on the table? Or will I take Uber or DoorDash or wait for tables?” Duffy made the announcement on ABC on Sunday.
