What the FAA nationwide ground stop says about old TDM gear

The FAA halted all flights across the US on Friday, November 13, after what Transportation Secretary Sean Duffy described as a fault in the old telecom network that links FAA facilities. Business Insider says the stop lasted about four and a half hours. Engadget reports it was lifted at 8:15 p.m. Eastern.

Duffy’s message was blunt: the old gear failed, and the new gear didn’t. For anyone who has lived through a legacy-network outage, that will sound familiar.

What did Duffy say actually failed?

Duffy said the legacy TDM telecom network that passes information between FAA facilities had routers that became overloaded with data. According to Engadget, he said they began sending inconsistent information at 3:36 p.m. Eastern. That’s his preliminary account. He said officials were still working out the details.

Don’t merge the two timestamps. Business Insider reports the ground stop itself was called at 3:54 p.m., after the routers had already started misbehaving.

The sources also describe the broken hardware differently. Engadget talks about TDM routers. Business Insider refers to old analog voice switches. Duffy also called the problem an “inconsistency” in FAA data systems that communicate with aircraft, and later tied it to a communication issue affecting all Air Route Traffic Control Centers. Those may be the same fault described from different angles. Nobody has said so.

Why one old layer can stop a whole country

Officials haven’t published a network diagram, so this part is my inference from what Duffy described. Still, the logic is easy to follow. A network that carries information between facilities isn’t a feature of one airport. Every center leans on it, and when it misbehaves, it misbehaves everywhere at once.

That matches Duffy’s remark that the issue touched all the Air Route Traffic Control Centers. It also explains why the failure was “inconsistent” data rather than no data. Inconsistent is worse. A dead link is obvious. A link that quietly delivers conflicting information makes controllers doubt everything that arrives over it. Stopping departures is a defensible response to that.

Duffy said the US did not lose all communications and radar, and that the FAA grounded flights out of an abundance of caution. The FAA itself said it acted because of extraordinary circumstances and for reasons of safety.

IT teams know this pattern: a shared dependency nobody wants to touch, still carrying critical traffic, and a failure that spreads because everything sits on top of it.

What the IP switch replacement changes

The FAA has been replacing analog voice switches with new voice communication systems built on IP switches. Duffy said the equipment already replaced was not affected and that the new IP switches did not go down. In his words, as Business Insider reported:

“It’s the old hardware that went down.” — Sean Duffy, via Business Insider

If that holds up, it’s the strongest argument for finishing the job. A partly modernized system is only as dependable as its oldest link. The new parts can run perfectly while the old ones set the ceiling for the whole network.

I’d keep one caution in mind. One day of the new switches staying up is encouraging, and it’s Duffy’s claim, but it isn’t proof that IP gear can’t fail. It does show that the replaced pieces weren’t the weak spot this time. How much legacy equipment is still in service hasn’t been reported. Engadget notes that lawmakers have previously appropriated $12.5 billion toward modernizing air traffic facilities.

Planes in the air stayed in the air

Duffy said about 3,000 flights were airborne when the stop began, and all landed safely using alternative systems. Retired Delta pilot Mark Stephens told Business Insider that planes already flying can continue on their flight plans and use backups such as digital links to air traffic control and airline dispatch.

Some flights did divert or turn back. Delta Flight 958, a Boeing 767 from Los Angeles to JFK, turned around at 4:11 p.m. and diverted to Cincinnati. A Delta flight from Atlanta to JFK diverted to Baltimore.

Engadget’s account mentions thousands of diversions and millions of stranded passengers. The other sources don’t back either claim with figures, so treat those as unsupported.

Why it matters for you

If you were flying Friday or Saturday, the damage is in the cancellations. Cirium counted more than 8,200 canceled flights on Friday alone, and more than 9,500 across Friday and Saturday as of late Friday night. ABC News later reported more than 12,500 for the two days. Those figures grew with time, so the totals depend on when they were counted. Chicago O’Hare led Cirium’s list with 205 cancellations, followed by Atlanta Hartsfield-Jackson with 195. Denver, Dallas, San Francisco, Boston and New York each logged more than 100.

The recovery is slow. On Saturday Duffy said operations were “slowly” returning to normal, and warned of more delays and cancellations while airlines reposition aircraft and crews. Business Insider says passengers have little recourse for meals or hotels, because the disruption wasn’t the airlines’ fault. Check your airline’s app and rebooking options before heading to the airport.

For IT and network people, the takeaway is older than aviation. Infrastructure debt doesn’t send a bill every month. It sends one big one, on a Friday afternoon.

That’s the argument Duffy is making in Washington. Engadget reports he has been trying to secure $30 billion more, while Business Insider says he and Homeland Security Secretary Markwayne Mullin called for $50 billion, up from $30 billion pitched in September. The sources disagree on the figure. Duffy also told the New York Times, as relayed by Engadget, that the system is “going to continue to fail,” and pressed Congress to pay for a fix.

We’ve also covered what broke in the FAA ground stop in plain English.

Cyberattack and AI theories

Officials say they’ve seen no evidence of either. Mullin said he had seen “zero evidence” of a cyberattack or an AI problem, and he and Duffy both ruled out AI and cybersecurity as the source of the fault. Engadget’s account adds that DHS was still looking and wouldn’t rule out a cyberattack entirely.

People online asked whether SMART, a new FAA AI tool built by ASI that began deploying this week, was involved. ASI said Friday’s issues were not based on or a result of SMART or any ASI product, and Duffy said SMART wasn’t at fault. Earlier Friday, Mullin had said officials were looking at whether the AI system was related. Both officials also said the incident was unrelated to the Microsoft outage that lasted more than 24 hours.

The SMART link was social-media speculation. Nothing in the record supports it.

What nobody has explained yet

The biggest gap is the mechanism. Why did the routers overload, and why now? Duffy couldn’t guarantee it wouldn’t happen again. A cause that hasn’t been pinned down can’t be reliably prevented.

Other open questions:

• How much legacy equipment remains in service, and what a full replacement costs. The sources cite $30 billion and $50 billion.
• Whether Congress will act on the funding request.
• The final cancellation and delay totals, and how long airlines need to move stranded passengers, crews and planes back into place.
• Whether passengers will see any compensation or rebooking relief.
• What changed between Mullin’s earlier comment about SMART and the evening statements ruling it out.

For scale, Business Insider says the previous nationwide ground stop was in January 2023 and lasted about 90 minutes. Before that, the last was on 9/11 in 2001. Engadget, citing Duffy and the New York Times, says this was the second longest after 9/11. That ranking wasn’t independently confirmed in the other sources.

Frequently asked questions

Why did the FAA ground all flights in the US?

According to Transportation Secretary Sean Duffy, old TDM telecom routers used to pass information between FAA facilities became overloaded and began sending inconsistent information. The FAA said it halted flights for safety reasons. Duffy called his account preliminary.

Was the FAA ground stop caused by a cyberattack?

Officials say they've seen no evidence of one. Mullin cited 'zero evidence' of a cyberattack, though Engadget reports DHS was still looking and would not fully rule it out.

How many flights were canceled?

Cirium counted more than 9,500 cancellations across Friday and Saturday as of late Friday night, including more than 8,200 on Friday. ABC News later reported more than 12,500. The totals grew over time.

Did new equipment fail too?

Not according to Duffy. He said equipment already replaced was unaffected and the new IP switches did not go down. Only old hardware failed.

Sources

This article was compiled from reporting by the following outlets. Links go to the original reports.

1. Engadget: FAA allows flights to resume after hours-long ground stop across the US
2. Business Insider: Travel chaos continues after the FAA's nationwide ground stop halted nearly 9,500 flights
3. ABC News: FAA ground stop live updates: More than 12,500 flights canceled Friday and Saturday