WASHINGTON (AP) — The Federal Aviation Administration said Wednesday that it would reduce air traffic by 10% across 40 “high-volume” markets beginning Friday morning 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 head of the FAA didn’t immediately identify which airports will be affected but said the restrictions would remain in place as long as necessary.

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 U.S. airports.

FAA Administrator Bryan Bedford, citing growing staffing pressures and safety reports 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.”

He and Duffy said they would meet with airline executives later Wednesday to determine how to implement the reduction in flights. Bedford said a list of the selected airports would be released sometime Thursday.

Airlines and passengers wait for information

The Associated Press on Wednesday sent requests for comment on the FAA’s decision to major U.S. airlines, including Delta, United and American Airlines.

Calls to the customer service hotlines at United and American got answered within a few minutes Wednesday afternoon, anxious passengers were not swamping the airlines with questions about the status of their upcoming flights.

Southwest Airlines said it was evaluating potential impacts to its flight schedule and would reach out as soon as possible to customers whose travel plans may be impacted.

“We continue to urge Congress to immediately resolve its impasse and restore the National Airspace System to its full capacity,” the carrier said.

AAA spokesperson Aixa Diaz said some travelers were adjusting their plans and considering driving to their destinations, but that’s not an option for everyone. She advised people with booked flights to try to stay informed by downloading their airline’s app and watching it for updates, or checking airport websites for the latest information.

Diaz recommended allowing plenty of time at the airport before a scheduled flight.

“It’s frustrating for travelers because there’s not much you can do. At the end of the day, you either fly or you don’t,” she said. “You go on your trip and you roll the dice and you show up at the airport, or you choose to drive. So you don’t have that many options.”

Data shows worsening weekend staffing

The FAA regularly slows down or stops flights from taking off toward an airport due to weather conditions, equipment failures and technical problems. Staffing shortages also may lead to slowed or halted departures if other personnel can’t fill in or another facility can’t absorb some of the work load.

Last weekend saw some of the worst staffing shortages of the shutdown, which became the longest on record early Wednesday.

From Friday to Sunday evening, at least 39 different air traffic control facilities announced there was some potential for limited staffing, according to an Associated Press analysis of operations plans sent through the Air Traffic Control System Command Center system. The figure, which is likely an undercount, is well above the average for weekends before the shutdown

During weekend periods from Jan. 1 to Sept. 30, the average number of airport towers, regional centers that oversee multiple airports and facilities that monitor traffic at higher altitudes announced the potential for staffing issues was 8.3, according to the AP analysis. But during the five weekend periods since the shutdown began on Oct. 1, the average more than tripled to 26.2 facilities.

Travel industry joins unions in urging shutdown’s end

Major airlines, aviation unions and the wider travel industry have urged Congress to end the shutdown.

Wednesday’s announcement came on the heels of Duffy warning a day earlier that there could be chaos in the skies next week if the shutdown drags on long enough for air traffic controllers to miss their second full paychecks next Tuesday.

Duffy said the FAA wanted to take a proactive approach instead of reacting after a disaster. He pointed to all the questions that arose after the deadly mid-air collision in January between a commercial jet and a military helicopter near Ronald Reagan Washington National Airport about why FAA didn’t recognize the risks and act sooner.

“We learned from that. And so now we look at data, and before it would become an issue, we try to assess the pressure and try to make moves before there could be adverse consequences,” Duffy said. “And that’s what’s happening here today.”

___

Associated Press journalist Christopher L. Keller contributed from Albuquerque, New Mexico. Yamat reported from Las Vegas and Funk reported from Omaha, Nebraska.