WASHINGTON (AP) — The Federal Aviation Administration last week said it was taking the extraordinary step of reducing air traffic by 10 percent across 40 “high-volume” markets to maintain travel safety as air traffic controllers exhibit signs of strain during the ongoing government shutdown.

The cutback stands to impact thousands of flights nationwide because the FAA directs more than 44,000 flights daily, including commercial passenger flights, cargo planes and private aircraft. The agency didn’t immediately identify which airports or cities will be affected but said the restrictions would remain in place as long as necessary.

“I’m not aware in my 35-year history in the aviation market where we’ve had a situation where we’re taking these kinds of measures,” FAA Administrator Bryan Bedford said at a news conference.

Air traffic controllers have been working unpaid since the shutdown began Oct. 1, and most have been on duty six days a week while putting in mandatory overtime. With some calling out of work due to frustration, taking second jobs or not having money for child care or gas, staffing shortages during some shifts have led to flight delays at a number of airports.

Bedford, citing increased staffing pressures and voluntary safety reports from pilots indicating growing fatigue among air traffic controllers, said he and U.S. Transportation Secretary Sean Duffy did not want to wait until the situation reached a crisis point.

“We’re not going to wait for a safety problem to truly manifest itself when the early indicators are telling us we can take action today to prevent things from deteriorating,” Bedford said. “The system is extremely safe today and will be extremely safe tomorrow. If the pressures continue to build even after we take these measures, we’ll come back and take additional measures.”

Airline industry analyst Henry Harteveldt, who is president of Atmosphere Research Group, said he thinks the government may have bungled the announcement by not meeting with airlines first and giving them more time to adjust schedules made months in advance.

“To tell airlines you’ve got 48 hours to rebuild your schedules at 90 percent of what you’ve got isn’t much time, and it’s going to result in a lot of chaos,” said Harteveldt, who was waiting to hear if his own flight from San Francisco to Dallas would be canceled. He added that the Trump administration may be using aviation safety “to force the two sides in Washington back to the negotiating table to resolve the shutdown.”

The cuts could represent as many as 1,800 flights and upward of 268,000 seats combined, according to an estimate by aviation analytics firm Cirium.