US halts all air traffic after router fault in copper-to-fibre upgrade

US Transportation Secretary Sean Duffy blamed a router fault during a copper-to-fibre upgrade for the nationwide ground stop that halted all air traffic inside the United States, telling a news conference in Washington, DC, on Saturday that the fault lay either with the contractor or with the equipment.

The maintenance was routine, carried out on Friday at a "very remote location" on an antiquated telecommunications system, Duffy said. The router then began flooding other routers in the air traffic control network. "We had 1,000 connection attempts every four to five seconds," he said.

Radar feeds and communications between controllers and aircraft were disrupted, and the Federal Aviation Administration shut the airspace. "Your safety is paramount," Duffy said.

The contractor was L3Harris, a US-based aerospace and defence company tasked with modernising the FAA's communications system. Duffy said the agency was trying to establish "whether we had incompetence" — installer error by L3Harris — "or did they install a faulty router?" He added: "We haven't determined what the fault was," and said L3Harris "didn't meet the moment". "They own this network," he said. "They're our prime contractor."

FAA Administrator Bryan Bedford said the outage was an equipment error. "We see zero evidence of anything nefarious, and zero evidence of anything AI-related," he said. Duffy said the government did not believe a cyberattack was involved, and that once the work at the location was isolated, "all of our systems came back online".

The stop was the longest and only the second nationwide halt since 9/11. Bedford said crews and aircraft were out of position for 12,000 flights, and that the FAA expected 4,000 to 5,000 of the 41,000 flights scheduled for Saturday to be cancelled. Full schedule integrity is expected by the end of Sunday. "I do think the worst is behind us," Bedford said.

A root cause analysis will be published when it is available, the FAA said. L3Harris has not responded to a request for comment on the allegations.