The Federal Aviation Administration has lifted the longest nationwide ground stop of flights since the Sept. 11, 2001, attacks, after a communications problem halted departures for more than four hours on Friday, the BBC and NPR reported. The FAA's first notice, at 3:54 p.m. Eastern time, said all flights departing within the United States were grounded until further notice. More than 3,500 aircraft were already in the air; some were diverted and others continued to their destinations. Skies reopened at 8:15 p.m. Eastern. FlightAware recorded more than 8,500 delayed flights and nearly 8,000 cancellations on Friday. All U.S.-bound traffic from Eurocontrol's 42 member states, including the United Kingdom, was suspended. Homeland Security Secretary Markwayne Mullin said there was no indication of a cyber-attack and that everybody was safe.
On Saturday, Transportation Secretary Sean Duffy said the stop was declared after an error during work by contractor L3Harris, which was updating an old FAA telecommunications line and changing copper wire to fiber at least one remote facility. Duffy said the routers in those facilities were manufactured in 2001. "Virtually every single institution in America has gone from copper to fiber, from analog to digital," he said. "Just maybe the FAA is the last one to be doing this work because the investments haven't been made, but this is not complicated." The agency is still investigating what started flooding other routers in the air traffic control system. "What we're working to determine was whether we had incompetence, meaning was it user error, installator error from L3Harris, or did they install a faulty router?" Duffy said. L3Harris did not immediately respond to NPR. FAA Administrator Bryan Bedford said there was no evidence of anything nefarious or of an AI-related issue.
Duffy had said on Friday that facilities experienced "intermittent" outages of radar and communications, blaming "old switches, old routers." Some flights were later allowed to leave San Francisco International Airport before the national stop was fully lifted. On Saturday morning the system was back online and returning to normal, Duffy said, though delays and cancellations would continue. Bedford said airline partners believed they would have "full schedule integrity by the close of business on Sunday." Duffy told reporters Friday night he thought the system would be "back up and operational as we come into the heat of travel during Thanksgiving."
The verified picture is an equipment-and-upgrade failure, a ground stop of more than four hours, and a still-open inquiry into whether the mistake was human or a faulty router — not a confirmed attack, and not a guarantee that Sunday schedules will be clean.