NEW YORK — Air travel across the U.S. Northeast began returning to normal Monday evening after a major communications failure at a Federal Aviation Administration air traffic control facility in Philadelphia disrupted operations at several major airports.

The disruption began after the primary communications circuit at the Philadelphia Terminal Radar Approach Control, known as Philadelphia TRACON, failed. When officials attempted to switch to the backup system, they discovered that a backup fiber-optic line had also been accidentally damaged during construction work in New Jersey.

The combination of the two failures affected radar and communications used by air traffic controllers, forcing the FAA to impose ground stops and other restrictions at several airports.

Newark Liberty International Airport was among the hardest hit. According to flight-tracking data cited by the Associated Press, more than 600 flights at Newark were canceled. Philadelphia International Airport also reported more than 200 cancellations, while significant disruptions affected John F. Kennedy International Airport, LaGuardia Airport and other airports in the region.

Transportation Secretary Sean Duffy announced Monday evening that the damaged communications lines had been repaired and that normal operations were beginning to resume across the Northeast. However, he warned that it would take additional time to clear the remaining delays and advised travelers to check directly with their airlines.

The outage was traced in part to construction activity in New Jersey. Verizon said contractors working near its telecommunications infrastructure accidentally cut a fiber-optic cable. New Jersey Transit also confirmed that a construction crew had accidentally severed a fiber line while working near utility markings.

The disruption occurred as world leaders and government officials were arriving in New York for the United Nations General Assembly. Canadian Prime Minister Mark Carney’s travel was affected by the outage, according to the Associated Press.

Flight-tracking company FlightAware reported thousands of delays and cancellations across the country as the Northeast disruption caused aircraft and crew schedules to fall out of position. Reuters reported that approximately 7,000 flights were delayed or canceled nationwide, including around 1,400 at the three major New York-area airports.

The incident has also renewed attention on the age of the U.S. air traffic control system. Philadelphia TRACON has experienced previous technical problems, including communications disruptions that affected flights around Newark.

FAA officials have been working on a broader modernization program designed to replace older communications and air traffic control infrastructure. Transportation officials have said the latest outage demonstrates the importance of upgrading aging systems and maintaining reliable backup connections.

Despite the restoration of the telecommunications network, travelers continued to face delays as airlines worked to reposition aircraft and crews and restore normal schedules.

Passengers traveling through affected airports were advised to check their flight status before heading to the airport and to contact their airlines regarding cancellations, delays or rebooking options.

Sources: Associated Press, Reuters, CNN.