A construction crew working on an Amtrak project in New Jersey accidentally severed a fiber-optic cable Monday, contributing to a telecommunications failure that disrupted Federal Aviation Administration operations and temporarily halted incoming flights at several major airports across the Northeast, Transportation Secretary Sean Duffy said.

The primary communications circuit at the FAA’s Philadelphia Terminal Radar Approach Control facility had already failed when controllers attempted to switch to a backup system and discovered that the fiber line had also been cut. The facility handles air traffic for major airports in the region, including Newark. FAA Administrator Bryan Bedford said the damaged backup line could take about 13 hours to repair, while crews work to install a replacement for the failed primary circuit.

The outage forced the FAA to pause incoming flights at Newark Liberty International Airport, John F. Kennedy International Airport, LaGuardia Airport, Philadelphia International Airport and Teterboro Airport at various points Monday. Flights were later resumed at LaGuardia and Philadelphia, while restrictions remained in place at Newark, JFK and Teterboro when Duffy provided his initial update.

The disruption spread beyond the affected airports as flights were diverted or held at their departure points. More than 5,600 flights nationwide had been delayed or canceled by Monday afternoon, including roughly 1,200 at the three major New York-area airports, according to FlightAware data cited by Reuters.

Duffy said the incident highlights the need to continue replacing aging FAA communications infrastructure. The Transportation Department has been working on a broader modernization effort, including additional telecommunications connections and upgraded fiber-optic systems designed to provide greater redundancy in the event of an outage.

The incident occurred as President Donald Trump and foreign leaders arrived in New York for the United Nations General Assembly, adding to the strain on one of the country's busiest air travel corridors. FAA officials said flights would not fully resume until the agency could verify that the airspace and communications systems were operating safely.

There was also some uncertainty over which railroad construction crew was responsible. Duffy attributed the cut to an Amtrak crew, while New Jersey Transit said a construction crew working on its Delco Lead project between New Brunswick and North Brunswick severed the cable at about 9:45 a.m. The circumstances surrounding the damage remain under investigation.