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A Routine Copper-to-Fiber Swap at One Remote FAA Site Set Off Friday's Nationwide Ground Stop, Duffy Says

Transportation Secretary Sean Duffy says a router installed during an L3Harris upgrade flooded the air traffic control network with connection attempts. The FAA is still working out whether the cause was a bad router or human error, and Duffy is using the outage to press Congress for $50 billion.

DailyMech Staff

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A Routine Copper-to-Fiber Swap at One Remote FAA Site Set Off Friday's Nationwide Ground Stop, Duffy Says
bernswaelz / Pixabay — Pixabay Content License

Airport control tower with a white geodesic radar dome on top, set against a clear blue sky

Illustrative photo of an airport control tower with a radar dome. It is not an FAA facility and was not taken during the Nov. 13 ground stop.

The four-hour shutdown of American air travel on Friday did not start with a hacker, a storm or an AI system. According to the federal officials in charge, it started with a wiring job.

At a press conference on Saturday, Nov. 14, Transportation Secretary Sean Duffy said the nationwide ground stop began during "routine maintenance" at a remote Federal Aviation Administration site, where L3Harris, a longtime FAA contractor, was replacing copper wire with fiber optic cable. After the upgrade, a newly installed router began flooding the rest of the air traffic control network, TechCrunch and The Verge reported.

What officials do not yet know is why. "What we're working to determine was whether we had incompetence — meaning, was it user error or installator error from L3Harris? Or did they install a faulty router?" Duffy said, according to TechCrunch.

At a glance

Item Detail Source
What happened Router overloaded a critical FAA communication network after an upgrade Duffy, via TechCrunch
Work under way L3Harris replacing copper wire with fiber at a remote FAA site Duffy, via TechCrunch, NPR
Scale of the flood About 1,000 connection attempts every 4 to 5 seconds FAA acting CTO Rebecca Guy, via TechCrunch; Duffy, via The Verge
Root cause Not yet determined; analysis under way FAA, via TechCrunch
Friday cancellations More than 9,000, with nearly 25,000 delays (FlightAware) NPR
Saturday cancellations More than 4,000 by Saturday morning, 18% of U.S. departures (Cirium) NPR
Funding ask $50 billion from Congress Duffy, via Politico

How a wiring job became a ground stop

The details came from Duffy and Rebecca Guy, the FAA's acting chief technology officer. Guy said that when the network became unstable, engineers went looking for the cause and "saw two places that were actually pinging our network at a very high rate — a thousand connections over every four to five seconds," according to TechCrunch. The FAA disabled both "right away" and was able to stabilize the network, she said, and the agency is now doing a root cause analysis.

Duffy said the flood disrupted radar feeds and communication with planes, The Verge reported. Bloomberg Government reported that systems came back online after the FAA isolated the work at the site.

The secretary said the copper line was so old that it was being discontinued, which forced the upgrade, according to The Verge. He described the job as "pretty straightforward work" at "a very remote location." He also told reporters, according to NPR: "When I tell you that we're using old equipment, we're using old equipment."

That explanation adds detail to Friday's more general account, when Duffy blamed overloaded switches and routers and no official cause had been given, as DailyMech reported at the time.

Why at 3 p.m. on a Friday?

One obvious question was timing. Asked why the work happened on a Friday afternoon, Duffy said that "switchovers" at big airports are done late at night, but that remote switchovers take place during the day, according to TechCrunch. "There will be reevaluation of when we do this work," he said.

L3Harris did not immediately respond to NPR's request for comment. DailyMech did not hear from the company before publication.

Not hackers, and not AI

Officials took care to rule out two theories that had spread online. FAA Administrator Bryan Bedford said the agency sees "zero evidence of anything nefarious and zero evidence of anything AI-related," TechCrunch reported. "We want to be clear that we have an equipment issue, and we're working through what this defective piece of equipment was," he said.

The AI question had a specific source. Just days before the outage, the FAA said it would use SMART, an $875 million AI-based traffic-flow advice system, across all 22 of its en route centers, Ars Technica reported. The controllers' union has said it was not involved in designing or testing it. NPR reported that Air Space Intelligence, which makes SMART, said the ground stop "is not based on or a result of the SMART system." When Homeland Security Secretary Markwayne Mullin was asked whether AI was to blame, he replied, "We call it SI around here, remember? SI," according to TechCrunch.

The damage

The disruption was one of the largest since the Sept. 11, 2001, attacks. TechCrunch called it only the third nationwide ground stop of the 21st century. The last one, in 2023, came after contract workers accidentally deleted files in the NOTAM system that warns pilots of hazards, NPR noted.

The numbers depend on the tracker and the hour. NPR, citing FlightAware, said nearly 25,000 flights were delayed and more than 9,000 canceled on Friday. Cirium counted more than 8,200 cancellations Friday evening, according to TechCrunch. By Saturday morning, more than 4,000 flights had been canceled, 18% of departures from the U.S., NPR said, citing Cirium. Bedford said schedules should be back to normal by Sunday evening and that passengers would be rebooked or get a full refund, though he told people to contact their airlines directly.

The money fight

Duffy used the briefing to renew his push for money. Politico reported that he is calling for $50 billion from Congress to upgrade the system, after lawmakers were lukewarm to his earlier $30 billion request. "We're gonna have a great end-of-the-year Christmas present for the American people," he said, according to Politico. "We're gonna get a chunk of money."

NPR noted that Congress approved $12.5 billion in July 2025 to modernize air traffic control. Bedford said that money has already replaced 70% of copper communications with fiber. "Virtually every single institution in America has gone from copper to fiber, from analog to digital," Duffy said, according to NPR. "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."

Why it matters

The explanation shows the risk of modernizing a network while it is still running. Swapping copper for fiber is meant to make the system sturdier, but Friday shows how one misbehaving device at one site can, on a tightly linked network, ground flights across the country. Two things will decide how much this fix improves things: whether the FAA isolates failures better as it upgrades, and when it schedules the work.

It also puts a contractor in the spotlight. By naming L3Harris and raising "incompetence," Duffy has made the root cause analysis a question of blame as well as engineering.

What to watch

Watch for the FAA's root cause analysis, and whether it points to a faulty router, a configuration mistake or a design that let one site affect the whole network. Watch for L3Harris's response, any changes to when the FAA schedules this kind of work and whether Congress moves on Duffy's $50 billion request.

How we reported this

This is a follow-up to DailyMech's Nov. 14 story on the ground stop, which was published before officials gave a cause. DailyMech read TechCrunch's and The Verge's reports on Saturday's briefing, NPR's report and Ars Technica's report on the SMART system in full. Politico's and Bloomberg Government's reports were read only up to their paywalls. Statements by officials are quoted as those outlets reported them. DailyMech contacted no one for this article.

Published November 14, 2026. Facts checked against the cited sources by DailyMech's AI writer.

Sources

DailyMech used AI tools to research and draft this article. Facts were checked against the cited sources by DailyMech's AI writer, not by a human editor.

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