On a Friday afternoon in mid-November, the sky over the United States went quiet, as aircraft across the continent were held on the ground for more than four hours. It was the longest such halt since the days after 11 September 2001, a reminder of how much modern travel rests on old machinery being carefully rebuilt. A contractor replacing aging copper lines with fibre triggered the failure, and officials are still working out whether the fault lay in human error or in faulty parts. For now the story is one of fragile infrastructure meeting a country still deciding how much it is willing to pa
Copper-to-fibre upgrade blamed for US nationwide flight ground stop; cause still under investigation
More than 3,500 flights were cancelled and 2,000 delayed, with some passengers left stranded inside planes on the tarmac unable to take off or return to gates.
For more than four hours, nothing left the ground.
Mark
Start with the basics. What actually stopped the planes?
Mimi
A router being worked on during a copper-to-fibre upgrade started flooding other air traffic control systems. That disrupted communication with aircraft, and the government closed the airspace for safety.
Mark
So it was a maintenance job, not an attack.
Mimi
That's the official position. Transport Secretary Sean Duffy says they don't believe it was a cyber-attack, and the FAA's Bryan Bedford says there's zero evidence of anything nefarious or AI related.
Luke
Worth noting those are officials' statements while the investigation is still open. Duffy himself said it's ongoing. "Does not believe" is not the same as "has ruled out."
Mark
And the contractor, L3Harris?
Mimi
It says it had finished over 70% of the modernisation work before the shutdown and is supporting the FAA's investigation.
Luke
That 70% figure comes from the company, so it's their account. And the core question is unanswered: Duffy said they're trying to find out whether it was incompetence or faulty equipment. Nobody has said which.
Mark
What did it cost travellers?
Mimi
Over 3,500 cancellations and more than 2,000 delays on Saturday per Flight Aware, plus passengers stuck on tarmacs.
Luke
Those are a tracking site's counts, and the disruption was still continuing, so the totals will likely change.
Mark
And what comes next?
Mimi
Duffy says it could recur without congressional approval of the $30.1bn Trump requested. Former TSA head John Pistole called the four-and-a-half-hour recovery resilient, but asked what stops it happening tomorrow.
The Pulse
- A single router under upgrade sent a flood through air traffic control systems, and within hours the entire national airspace was frozen.
- More than 3,500 flights were cancelled and thousands more delayed, leaving some passengers trapped on tarmacs unable to take off or return to gates.
- Investigators are sifting through contractor L3Harris's work to decide whether incompetence or defective equipment caused the breakdown, while officials rule out a cyber-attack.
- Transport Secretary Duffy is pressing Congress to approve $30.1bn in air traffic control upgrades, warning that the same failure could strike again.
- Service is slowly restarting, but the question of whether tomorrow's skies will hold remains open.
On a Friday afternoon in mid-November, the sky over the United States went quiet, as aircraft across the continent were held on the ground for more than four hours. It was the longest such halt since the days after 11 September 2001, a reminder of how much modern travel rests on old machinery being carefully rebuilt. A contractor replacing aging copper lines with fibre triggered the failure, and officials are still working out whether the fault lay in human error or in faulty parts. For now the story is one of fragile infrastructure meeting a country still deciding how much it is willing to pay to keep it steady.
At 15:54 Eastern time on Friday 13 November, aircraft across the continental United States were told they could not take off. For more than four hours, nothing left the ground. It was the longest nationwide ground stop since the days after the attacks of 11 September 2001, and only one other has been ordered since.
By Saturday the damage was still spreading. More than 3,500 flights were cancelled and over 2,000 delayed, and some passengers sat inside planes on the tarmac, unable to take off or get back to the gates. Some international flights were allowed to leave, in an effort to clear space.
Transport Secretary Sean Duffy said the trouble began during a copper-to-fibre upgrade carried out by the contractor L3Harris. A router being worked on began flooding other air traffic control systems, disrupting communication with aircraft, and the government shut the airspace for safety. Duffy called the American telecom system incredibly old, and said the copper involved was being discontinued. Why the work failed is still unknown: officials are testing whether the cause was contractor incompetence or faulty equipment. L3Harris says it had completed more than 70% of the modernisation and is cooperating with the investigation.
Officials were firm that a cyber-attack is not suspected, and the FAA said it saw no evidence of anything nefarious or AI-related.
Duffy warned that the failure could recur unless Congress approves $30.1bn requested by President Trump for air traffic control upgrades. John Pistole, a former TSA administrator, called the four-and-a-half-hour restart a sign of resilience, but asked the question that lingers: what says it will not happen again tomorrow?
At 15:54 Eastern time on Friday, 13 November, aircraft across the continental United States were told they could not take off. For more than four hours, nothing left the ground. It was the longest nationwide ground stop since the days after the attacks of 11 September 2001, when all flights were banned from departing for several days. Only one other nationwide ground stop has been ordered since then.
By Saturday the effects were still spreading. According to the tracking website Flight Aware, more than 3,500 flights in the US were cancelled and over 2,000 delayed that day as the knock-on disruption continued. Officials expect it to last for days. In some cases passengers were stuck inside planes on the tarmac, unable to take off and unable to return to the gates. Some international flights were allowed to leave US airports, in an apparent effort to clear space.
Transport Secretary Sean Duffy told a news conference that the problem followed a copper wire upgrade. A contractor, the technology provider L3Harris, was carrying out maintenance to switch part of the system from copper wire to fibre. A router being worked on began flooding other air traffic control systems, Duffy said, which created communication problems with aircraft. The government shut down the airspace for safety reasons.
Duffy described the American telecommunications system as incredibly old, and said the copper wire involved was so outdated that it was being discontinued. What remains unresolved is why the work went wrong. Duffy said the government is trying to determine whether the cause was "incompetence" on the part of the company doing the upgrades, or faulty equipment.
Officials were firm on what it was not. Duffy said the government does not believe a cyber-attack was responsible, though an investigation is still under way. Bryan Bedford, who heads the Federal Aviation Administration, said at the same news conference that the agency sees zero evidence of anything nefarious and zero evidence of anything related to AI.
On Saturday, L3Harris said it had completed more than 70% of the work to modernise the communications infrastructure before the shutdown. In a statement, the company said it is supporting the FAA's investigation into the conditions that led to the 13 November ground stop, and that it takes the stop and its impact on travellers, airlines and air traffic operations seriously.
Duffy warned that a similar problem could happen again unless Congress approves upgrades to air traffic control infrastructure. President Donald Trump has requested $30.1bn for that purpose. Both chambers of Congress are currently controlled by the Republican Party.
John Pistole, a former TSA administrator, told the BBC that restarting the system within four and a half hours was good news and showed resilience. But he asked the question that hangs over the episode: what is to say it will not happen again tomorrow? The answers now depend on the FAA's investigation into the contractor's work and on whether Congress acts on the funding request.
Notable Quotes
We see zero evidence of anything nefarious, and zero evidence of anything AI related.— Bryan Bedford, FAA head
The fact that they were able to get it restarted in four-and-a-half hours is good news, but what's to say it's not going to happen tomorrow?— John Pistole, former TSA Administrator (paraphrased)
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