FAA ground stop traced to a single router as L3Harris copper-to-fibre work flooded the network

U.S. Transportation Secretary Sean Duffy said on Saturday that the nearly five-hour nationwide shutdown of American aviation on November 13 was likely caused by a single router installed by government contractor L3Harris. The company was carrying out routine maintenance at a remote Federal Aviation Administration site, switching telecommunications lines from old copper wire to fibre, when the router began flooding other routers in the system with connection requests, overwhelming communications at 17 of the FAA's 22 en route centres. The FAA ordered a nationwide ground stop, disrupting more than 20,000 flights. Officials stressed that it has not been determined whether the fault was installer error or defective equipment, and there is no evidence of a cyberattack.

More than 1,000 connection attempts every four to five seconds

Duffy said the trouble began at about 3:36 p.m. ET on November 13, when radar and communications data at air traffic facilities began producing inconsistent readings; shortly before 4 p.m., the FAA issued a nationwide ground stop, citing 'extraordinary circumstances' and 'reasons of safety'. Duffy later explained that the router involved was sending more than 1,000 connection attempts to other routers every four to five seconds, disrupting radio contact with pilots and some radar feeds. The ground stop lasted more than four hours and was lifted at about 8:45 p.m. Officials said there may have been problems with routers in Arkansas and Texas.

25-year-old routers that were due to be replaced in 2006

Duffy said the routers being replaced are about 25 years old and were supposed to be replaced in 2006. The FAA spends $1 billion a year maintaining its old copper-wire system and is racing to replace it with modern fibre-based communications. Congress has provided $12.5 billion to upgrade the badly ageing air traffic control and telecom system. L3Harris said it has completed more than 70 percent of the planned conversion from legacy copper to fibre optics and is supporting the FAA investigation. 'This was an FAA system that didn't meet the moment,' Duffy said. He also said he plans to ask Congress on Monday for $50 billion in upgrade funding.

More than 20,000 flights disrupted; normal service due Sunday night

Reuters cited officials as saying more than 20,000 flights have been disrupted since Friday; other tallies put Friday's delays at more than 10,000 flights and cancellations at more than 9,100, affecting over two million passengers. Airlines expect full schedules to resume by Sunday night. It was the first nationwide ground stop since January 2023, when a key FAA computer system malfunctioned. Airports including Montreal also suspended flights to and from the United States on Friday.

Installer error or faulty equipment still undetermined

Duffy said the authorities are 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.' The FAA said communications did not go down but produced instability in data at the centres. Homeland Security Secretary Markwayne Mullin said there was no indication yet of a 'nefarious attack', and the FBI does not believe a hacker was involved. L3Harris said in a statement that it is 'supporting the FAA in its investigation to understand the conditions that led to the Nov. 13 ground stop of our nation's air travel.'

(File photo: an airport air traffic control tower.)