By JOSH FUNK AP Transportation Writer

Hundreds of flights were canceled in the U.S. Northeast due to technical problems at a key regional air traffic control center, hitting every major airport in the New York City area for several hours Monday before the federal transportation chief said damaged data lines were fixed and operations were resuming.

The primary communications line failed at a key Federal Aviation Administration facility in Philadelphia and the backup fiber optic line was inadvertently severed by railroad construction workers. That left controllers without radar or communications during the day.

Transportation Secretary Sean Duffy said in an online post that the primary and backup lines were fixed by Monday evening and all airports in the Northeast were operating again. But significant delays were expected to continue through the evening hours.

Hundreds of flights were canceled at the Newark, LaGuardia, Kennedy and Philadelphia airports. By Monday evening, flights were resuming at all those airports. Some airlines were allowing customers to change flights without charge. The FAA advised travelers to check the status of their flights before heading to the airport.

The outage happened just as President Donald Trump and numerous foreign leaders were flying into New York City for the United Nations General Assembly.

The technical problems stem from the same FAA facility in Philadelphia that caused numerous disruptions at Newark Liberty International Airport in the spring of 2025.

Regional control centers like these have two lines that carry radar and communications data in and out: the primary and the backup. The FAA said a circuit on the primary failed Monday morning, and when the system tried to switch to the backup, workers discovered that the fiber optic line had been cut.

Earlier in the day, Duffy said an Amtrak construction crew was to blame. Amtrak, however, pointed to a New Jersey Transit construction crew that was working in the area between Newark and New Brunswick, New Jersey.

FAA administrator Bryan Bedford told reporters earlier that the agency had focused efforts on fixing the primary connection as soon as possible by installing a new circuit on the primary line, while also working to repair the backup fiber optic line. Verizon said at the time that its technicians were also working to restore service as soon as possible.

Bedford earlier described the fiber break as “massive,” saying it would take several hours to repair, according to a video posted online by a CBS transportation reporter.

The primary circuit that failed is due to be replaced as part of the overhaul of the nation’s air traffic control system.

Also Monday, the FAA began testing a new computer system that uses AI to help predict schedule conflicts and weather issues to help air traffic controllers reroute traffic. But that system is initially being tested only in the Washington, D.C., area, so it did not appear to be linked to the outages.