Shortly before 4 p.m. Eastern on Friday, 13 November, the Federal Aviation Administration stopped every departure in the United States. Its notice cited "extraordinary circumstances and for reasons of safety." The airspace reopened at 8:15 p.m. ET, about four hours later. FlightAware counted nearly 7,000 flights delayed or canceled by Friday afternoon; by Saturday, CNBC reported more than 6,200 delays and 3,400 cancellations. Aircraft already in the air could land, and inbound international flights were handled case by case.
It was the first nationwide ground stop since January 2023, when the FAA's Notice to Air Missions system failed, and the second since the 11 September 2001 attacks. The 2023 stop lasted about 90 minutes; the FAA later found that contract personnel had inadvertently deleted files while synchronizing the system's primary and backup databases.
The cause is not settled, and the account moved during the evening
Transportation Secretary Sean Duffy's first statement named a "communication issue impacting all Air Route Traffic Control Centers." By the White House briefing that began fifteen minutes after the airspace reopened, there was a mechanism:
"Our switches, our routers actually got overloaded with data and they went down. And — I shouldn't say they went down; they started to give us inconsistency in the data from those routers. And because of that, we shut the system down."
He said the old hardware failed, not the new: "our new IP switches did not go down; it's the old hardware that went down." He asked Congress to fund the replacement, saying the president had asked for \$30 billion and "I want \$50 billion."
Homeland Security Secretary Markwayne Mullin, at the same briefing, gave a different and more specific account:
"What it appears to be right now is, as Secretary Duffy and FAA was going in and putting patches into the system, they were putting new equipment and new technology, and that new equipment, new technology just wasn't — it was overwhelming the older system."
The two are not flatly contradictory — new equipment can stay online while changes associated with it overload older equipment elsewhere — but they point at different things. Duffy emphasized that the new switches were fine and the old system is the problem. Mullin described the modernization work itself as what overwhelmed it. Duffy also conceded the limit of what officials knew: "we're still working on the details of what went wrong today."
Mullin called it "a telecommunication outage throughout FAA," said there was "no cyberattack" and "no indication of a nefarious attack," and declined to rule anything out: "You just can't rule out anything at this point."
The AI tool that had just gone nationwide
Three days before the failure, on 10 November, the FAA announced it was expanding SMART — Strategic Management of Airspace, Routes and Trajectories — to the airspace of all 22 en route centers, after a limited deployment around Washington, D.C. that began 21 September. SMART is a cloud-based system from Boston-based Air Space Intelligence; the FAA describes it as pulling in about 200 data streams to recommend flight schedules and routes, with FAA specialists reviewing the recommendations and local facilities deciding whether to act on them. The agency's 10 November statement said the tool had rerouted 180 flights in the Washington area, saving an average of 10 minutes and nearly 80 gallons of fuel per rerouted flight. It is part of a 12-year, \$875 million contract.
Duffy said SMART had nothing to do with it: "This is completely disconnected... this is not even plugged in. So, there's no possible way SMART would have impacted." Air Space Intelligence posted its own denial while the outage was still in effect: "The current ground stop is not based on or a result of the SMART system, any product of ASI or our integration with FAA and ATC."
Mullin did not rule it out. Asked about a possible link, he said, "We're looking at that," and said DHS was examining it through CISA. (He also corrected a reporter's "AI" to "SI" — "superintelligence," President Trump's preferred term.)
The worry predates the outage. Rep. Don Beyer (D-Va.), co-chair of the Congressional AI Caucus, whose district includes Reagan National, called on 21 September for the FAA to suspend SMART: "The FAA should not use my constituents as guinea pigs for an unproven AI air traffic control system." On 9 October, about 25 lawmakers — led by Reps. April McClain Delaney, Alexandria Ocasio-Cortez and Beyer, with Sen. Chris Van Hollen — asked the FAA to pause SMART at three Washington-area airports, pending safety evaluations and answers on training and oversight.
A second outage, with no established link
The FAA failure came a day after a separate global Microsoft 365 outage that began Thursday morning in Exchange Online, the service behind Outlook email for businesses, and spread to Teams, Copilot and SharePoint. Microsoft said it was a technical issue, not a cyberattack or AI agents, introduced during an earlier network capacity upgrade and surfaced after a more recent network change, and promised a full post-incident report. Mullin told reporters he saw no reason to connect the two — "Those are separate issues" — while declining to rule out a cyberattack on the FAA. Duffy said the FAA problem hit all 22 centers; Mullin said two areas could still communicate normally. Nothing published by Saturday established a link between the two outages.
The money arrived first
Hours before the ground stop, the White House and the Department of Transportation asked Congress for an additional \$30.1 billion for aviation infrastructure modernization, including \$10.1 billion for air traffic control. Congress had already approved \$12.5 billion over five years in July 2025 for ATC improvements and controller hiring. Whether more money would have prevented Friday's failure depends on which account is right: if the problem was new technology overwhelming the old system, a fully funded replacement still passes through the same transition.
What would settle it
- The FAA's own account of what failed, with the router and telecom logs and a timeline. As of Saturday there was none.
- CISA's findings on whether SMART or the modernization work contributed.
- Whether the 22-center SMART expansion is paused pending review — the question Beyer and the October letter asked before the failure.
- Microsoft's post-incident report, for the separate outage.
- What Congress does with the request: \$30.1 billion asked, \$50 billion demanded at the briefing, in a chamber that flipped in November.
Sources I read: AeroTime's timeline; The Hill on the SMART denial; GeekWire on the two outages and the 22-center expansion; Live and Let's Fly's account of the briefing, which carries the transcript quotes; FedScoop and Rep. Beyer's office on the September–October warnings. AP's article reached me through PBS's reprint; I did not read the full Roll Call transcript of the briefing.