FILE PHOTO: An ageing US air traffic control telecommunications system is under scrutiny after a suspected router failure disrupted more than 20,000 flights. | Photo Credit: Aaron Schwartz

A massive, nearly five-hour shutdown of the US aviation system that disrupted more than 20,000 flights since Friday may have been caused by a single router installed by government contractor L3Harris, government officials said on Saturday.

The incident is the latest example of problems with the ageing US air traffic control telecommunications system and the challenges of replacing outdated equipment while keeping existing communications systems operational.

The FAA’s ageing telecom systems have failed several times in recent years following accidental fibre-optic cable cuts, unintended deletion of files and a strong chemical smell caused by a melted component. Officials said the system could fail again until it is properly upgraded.

“This was an FAA system that didn’t meet the moment,” Transportation Secretary Sean Duffy said on Saturday.

L3Harris router suspected of triggering communications failure

Duffy said on Friday that L3Harris was conducting routine maintenance to switch telecommunications lines from old copper wires to fibre at at least one remote location. Officials told Reuters that there may have been problems with routers installed in both Arkansas and Texas.

“We’re working to determine whether we had incompetence, meaning was it user error or installer error from L3Harris, or did they install a faulty router? We haven’t determined what the fault was,” Duffy said.

L3Harris said it took the issue seriously and was “supporting the FAA in its investigation to understand the conditions that led to the Nov. 13 ground stop of our nation’s air travel.”

L3 noted that it had completed more than 70 per cent of the planned airspace communications conversion from legacy copper wires to a fibre-optic system.

The FAA spends $1 billion annually to maintain its old copper-wire system and is racing to replace it with more modern fibre-based communications.

“We need L3Harris or whoever provided that router to us to do a better job,” Duffy said, noting that “virtually every single institution in America has gone from copper to fibre, from analog to digital.”

Router connection attempts overloaded FAA communications

The issue began overloading communications at 17 of the FAA’s 22 en route centres across the country, prompting the agency to issue a nationwide ground stop because it could not identify the root cause.

Duffy said the new routers started flooding other routers with more than 1,000 connection attempts every four to five seconds, triggering communications problems involving aircraft and radar at FAA facilities.

Bedford said the FAA had to take action after it lost “the ability for those routers to communicate data.” The FAA is still trying to understand the root cause of the failure.

The FAA said communications did not go down but caused instability in data at the centres. The incident did not result in the centres going dark. The routers being replaced are about 25 years old, Duffy said, and were supposed to have been replaced in 2006.

Not the first time a technical failure has disrupted flights

Small mishaps leading to catastrophic consequences are not new to the US air traffic control network. A 2023 FAA nationwide ground stop that lasted 90 minutes and disrupted 11,000 flights was caused by a government contractor unintentionally deleting files.

That led to the first nationwide ground stop since the hijacked airplane attacks on September 11, 2001.

Friday’s outage occurred as a surge in travellers began weekend travel. Noting the poor timing, Duffy said officials would reevaluate when work is carried out at smaller facilities to prevent future disruptions.

FAA plans major investment to modernise ageing systems

The FAA received $12.5 billion from Congress to upgrade its badly ageing air traffic control and telecommunications systems, and Duffy has sought an additional $50 billion for air traffic control and airports.

Only last week, the FAA said it would replace outdated floppy disks used for weather and other critical information at more than 400 air traffic control facilities by the end of 2028.

The FAA relies on a telecommunications system that it is racing to replace, as well as decades-old Compaq computers and replacement parts bought on eBay.

In September, thousands of flights across the densely populated Northeast were delayed or cancelled due to the simultaneous failures of a circuit at a Philadelphia air traffic facility and the accidental severing of a fibre-optic cable in New Jersey by a construction crew.

The FAA has also been working for years to end a long-ridiculed, decades-old practice of air traffic controllers using paper flight strips to keep track of aircraft. However, adopting the change, which began in 2022, at 49 major airports will take until at least 2028.

Published on November 15, 2026