A FAULTY router installed by government contractor L3Harris may have triggered a massive shutdown of the United States aviation system that disrupted more than 20,000 flights, officials said.
The nearly five-hour disruption on Friday affected communications at 17 of the Federal Aviation Administration's (FAA) 22 en route air traffic control centres, forcing authorities to impose a nationwide ground stop over safety concerns.
Reuters reported that Transportation Secretary Sean Duffy said investigators were examining whether the incident resulted from human error, installation problems or a defective router.
"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," he said on Saturday.
Duffy said L3Harris had been carrying out routine maintenance to replace ageing copper telecommunications lines with fibre-optic connections at remote facilities, with potential router-related problems identified in Arkansas and Texas.
He said the new routers began flooding other devices with more than 1,000 connection attempts every four to five seconds, triggering communications instability involving aircraft and radar data at FAA facilities.
"This was an FAA system that didn't meet the moment," Duffy said.
The FAA clarified that communications had not completely failed and that its control centres had not gone dark, but data instability prompted the precautionary ground stop.
L3Harris said it was taking the incident seriously and assisting the FAA's investigation into the circumstances surrounding Friday's disruption.
The company said it had completed more than 70 per cent of the planned conversion of the airspace communications network from legacy copper wiring to fibre-optic technology.
The incident has renewed concerns over the condition of the US air traffic control infrastructure, which officials say requires urgent modernisation.
The FAA spends about US$1 billion annually maintaining its ageing copper-wire system, while the routers involved in the latest incident were about 25 years old.
Duffy said the agency needed contractors and equipment suppliers to improve their performance, noting that much of the country had already transitioned from copper-based and analogue systems to fibre and digital technology.
The latest disruption is not the first major failure involving the FAA's ageing infrastructure.
In January 2023, a nationwide ground stop lasting about 90 minutes disrupted approximately 11,000 flights after a government contractor accidentally deleted files from a critical system.
Other incidents have involved damaged fibre-optic cables, accidental infrastructure cuts and equipment failures.
In September this year, thousands of flights across the densely populated northeastern United States were delayed or cancelled following separate failures involving a circuit at a Philadelphia air traffic facility and a fibre-optic cable severed by a construction crew in New Jersey.
Congress has allocated US$12.5 billion towards upgrading the country's ageing air traffic control and telecommunications infrastructure, while Duffy has sought an additional US$50 billion for air traffic control systems and airports.
The FAA has also pledged to replace outdated floppy disks used to store weather and other critical information at more than 400 air traffic control facilities by the end of 2028. - November 15, 2026
