Copper-to-fibre upgrade error caused Friday nationwide ground stop, FAA says

The nationwide ground stop in the United States on Friday was declared after an error occurred while a contractor was updating old Federal Aviation Administration (FAA) telecommunications equipment, Transportation Secretary Sean Duffy said on Saturday. Initial investigations pointed to an issue with contractor L3Harris updating old technology at a remote location, he said.

Duffy said L3Harris, a longtime FAA contractor, was doing routine maintenance at at least one remote FAA location, changing copper wire to fibre. The routers in these facilities were manufactured in 2001, he said. Virtually every institution in America has gone from copper to fibre and from analogue to digital over decades, Duffy said, adding that the FAA may be the last to do this work because the investments had not been made, but that the work is not complicated.

L3Harris did not immediately respond to a request for comment. Duffy said the FAA is still investigating the exact error that started flooding other routers in the air traffic control system. It was straightforward work at a very remote location, he said; what they are working to determine is whether it was incompetence — user or installer error by L3Harris — or whether they installed a faulty router.

FAA Administrator Bryan Bedford, who joined Duffy at the briefing, said there was no evidence of anything nefarious or of AI-related issues. Duffy had said on Friday night that air traffic control facilities experienced intermittent outages of their radar and communications systems beginning earlier that afternoon, blaming old switches and old routers. Homeland Security Secretary Markwayne Mullin also said there was no evidence the issue was due to an attack.

For about four hours on Friday, thousands of flights at US airports were grounded. Nearly 25,000 flights were delayed and over 9,000 were cancelled on Friday, according to the flight tracking site FlightAware. The disruption seeped into Saturday morning, with more than 4,000 cancellations recorded — 14 percent of flights departing the US, according to aviation analytics firm Cirium.

The aviation system is back online and slowly returning to normal, Duffy said on Saturday morning, but delays and cancellations would continue. Based on what airline partners were saying, they believed they would be able to have full schedule integrity by the close of business on Sunday, Bedford said. Duffy told reporters on Friday night that he thought they would be back up and operational in time for the heat of travel during Thanksgiving.

This was only the second nationwide ground stop since the terrorist attacks of 11 September 2001. The US last issued a ground stop of this scale in 2023, when all US airports were shut down because of an outage in the NOTAM system, which alerts pilots and airports to real-time hazards. That outage prompted fears of a cyberattack, but the FAA later determined it was caused when contract workers inadvertently deleted critical files.

The FAA has recently begun rolling out an AI-enhanced software tool known as the SMART system as part of its overhaul of the national air traffic control system. But Air Space Intelligence, the company that makes the tool, said on social media that the current ground stop was not based on or a result of the SMART system, any of its products, or its integration with the FAA and air traffic control.