The primary circuit that failed is due to be replaced as part of a massive overhaul of the nation's air traffic control system.
PHILADELPHIA (WPVI) -- Damaged communications lines at a key air traffic control facility in Philadelphia had been repaired, allowing airports across the Northeast to resume operations after hours of disruptions, the nation's transportation secretary said Monday evening.
The Federal Aviation Administration issued two ground stops at Philadelphia International Airport, which halted hundreds of flights in the Northeast on Monday.
Hours after officials said the fix to replace the circuit in Philadelphia had not worked, leaving operations still halted at Philadelphia and Newark's airports, Transportation Secretary Sean Duffy updated Monday evening that the telecom lines have been repaired and "all airport operations in the Northeast are resuming."
"It will take some time to clear all existing delays, so please check with your airline for the latest information," he said on X.
More than 1,000 flights were canceled nationwide and over 6,000 were delayed on Monday, with Newark and Philadelphia hit the hardest.
The primary communications line at the Federal Aviation Administration facility in Philadelphia had failed earlier Monday, while the backup fiber optic line was inadvertently severed by construction workers. The failures left controllers without radar or communications for hours.
The outage brought commercial air traffic to a near-standstill at Newark Liberty International Airport for much of the day, with no commercial flights landing at the airport from about 9:40 a.m. to just after 5:20 p.m. local time, according to flight-tracking site Flightradar24.
More than 200 flights into and out of Philadelphia International Airport were also canceled, while disruptions hit LaGuardia and Kennedy airports in New York. By Monday evening, flights were resuming at 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.
Shannon Franke and her husband took a connecting flight from Nashville to Chicago when they found out their final Southwest leg home to Philadelphia was canceled. They had gone to Nashville to see the Philadelphia Eagles beat the Tennessee Titans 24-20 on a touchdown in the last seconds Sunday.
Stuck in Chicago, Franke said they lucked out finding a hotel room and decided to enjoy some deep-dish pizza.
"We're just making the best of it," Franke said. "If the Eagles would have lost ... it would have been so much worse."
The technical problems stem from the same FAA facility in Philadelphia that caused numerous disruptions at the Newark airport last spring.
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 the agency had focused 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.
The primary circuit that failed is due to be replaced as part of a massive 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.
The Associated Press contributed to this report.