The FAA blamed old routers for a 4-hour nationwide ground stop. The network behind them is halfway through a rebuild.
Dayton International's flights sat with everyone else's Friday. The AI tool the internet blamed was "not even plugged in," the transportation secretary said. The FAA said Tuesday it was running everywhere.
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Routers choked. Radar data went shaky. At 3:54 p.m. Friday, the Federal Aviation Administration told every airport in the country to stop sending planes up.
It held for 4 hours and 21 minutes. The FAA lifted the order at 8:15 p.m. (CNBC)
If you were booked out of Vandalia Friday afternoon, you weren't leaving on time.
What it did here
Dayton International told travelers that every departure was suspended until the FAA lifted the stop, according to the airport's statement published by WHIO. WHIO reported cancellations starting at DAY by 5:45 p.m.
At 10:11 p.m., WDTN reported many Dayton flights still canceled or delayed, with Saturday flights affected too. William Johnston's flight to Tampa was grounded. Zach Shafer sat on a runway in Orlando trying to get home. Some people waited at the airport. Some drove.
Down I-75 at CVG, cancellations stood at 19 as of 8:15 p.m. (Yahoo News)
Nationwide, the count kept moving all night. NPR, citing FlightAware, reported more than 7,000 cancellations and more than 8,000 delays as of 9 p.m. (NPR). ABC News put cancellations near 5,000 (ABC News). Transportation Secretary Sean Duffy said more than 3,500 planes were in the air when the order came and all of them landed safely (Scripps News). Medical flights kept flying (NBC4 Washington).
We asked Dayton International early Saturday for its final count.
What the government says broke
At a White House news conference Friday night, Duffy described the equipment as analog telecom. "Our switches, our routers, actually got overloaded with data," he said (NBC News). He said the newer switches held and the old ones went down. He said the FAA never lost all of its radar or radio, and stopped flights because the data was unstable.
CBS News heard something different. Multiple sources told CBS that an update to the private network connecting the air traffic control system caused a reboot, a crash and the outage. CBS said that network is operated by L3Harris, which did not immediately respond to CBS (CBS News).
An overload and a bad update are different failures. The FAA hasn't said which it was.
When reporters asked why the equipment overloaded on an ordinary Friday, Duffy didn't have a ready answer, NPR reported. He said it's "going to continue to fail" (CNBC) and asked Congress for billions more.
The network nobody is talking about
The FAA's own paperwork has been saying this for years.
The FAA's main phone and data network is called FTI. It carries voice, radar and data between FAA sites. The Transportation Department's 2025 modernization plan says it dates to 2002 and leans on 1960s TDM technology (DOT).
The old network is being rebuilt while it runs. L3Harris runs FTI as a managed service and owns the equipment, according to its own program sheet. In May, the company said it had finished more than half the job of swapping copper lines for fiber across FAA sites (L3Harris). The Government Accountability Office counted the same thing in September: as of May, 2,560 of 5,170 old copper lines had been replaced (GAO-26-107992).
The network meant to replace FTI for good is called FENS. Verizon won that job in March 2023. On Aug. 11, the FAA handed the lead to AT&T without a new competition, saying another bid would put a December 2028 deadline at risk. Verizon stayed on in a supporting role (Inside Towers, Washington Technology).
So on Friday, the network carrying the load was halfway through a rebuild, and the company picked to build its successor had changed three months earlier.
FAA officials told GAO that replacing 450 voice switches is the riskiest part of the first phase. GAO said the cost estimate leaves out most of what the new system will cost to run, and the Transportation Department only partly agreed to fix its cost and schedule planning (GAO).
This has happened before. On Nov. 19, 2009, FTI went down for about five hours and grounded hundreds of flights nationwide. The Transportation Department's inspector general found the contractor's configuration and procedural errors caused it, and warned the risk would remain as new services were added (DOT OIG).
None of that says what broke Friday. It says what to ask.
The AI question
The internet had its answer early.
We pulled every Reddit post from 3 p.m. to midnight Friday in 20 subreddits. The first post tying the stop to AI went up at 4:30 p.m. in r/news, about 36 minutes after the order. It was a Gizmodo story about the FAA's new AI tool, written before the outage. By 5:17 p.m. that link had been posted at least seven more times.
The tool is called SMART. It's built by Air Space Intelligence, a Boston startup. It suggests reroutes. FAA specialists in Washington check the suggestions and send them to the national command center, and facilities can accept or decline them. The FAA has said SMART can't take control of an aircraft (Airways).
The FAA told Flying magazine on Tuesday that SMART was active in the airspace of every one of its en route centers (Flying).
At an afternoon news conference Friday, Homeland Security Secretary Markwayne Mullin said officials were looking into a possible link (GeekWire). At 5:34 p.m., the company posted on Twitter that the stop had nothing to do with SMART or its work with the FAA. That night, Duffy said SMART was "not even plugged in" (The Hill).
Active everywhere on Tuesday. Not plugged in on Friday. We asked the FAA which is right.
The tool had critics before Friday. More than two dozen lawmakers wrote the FAA on Oct. 9 asking it to pause the rollout until questions about testing, training and oversight were answered (AvWeb). The air traffic controllers' union told Flying it had not been involved in designing, testing or rolling out SMART (Flying).
Then there's the contract. Most coverage calls it $875 million over 12 years. The FAA's contract with Air Space Intelligence on USAspending, number 693KA726C00064, shows $23,340,500 spent so far, running June 2026 to June 2038 (USAspending). The $875 million isn't in that record. We asked where it comes from.
That contract also pays for a replacement for the FAA's traffic flow management system, the system that runs ground stops. GAO says the current one is expected to become untenable by 2027. There is no evidence that system played any part Friday. We asked anyway.
What we asked the FAA
Which centers failed first? Was Indianapolis Center, which runs the high-altitude "Dayton High" sector over us, one of them? (LiveATC)
Was anyone working on the network Friday? The FAA, L3Harris, Verizon or AT&T?
Was SMART running on anything that failed?
Will the inspector general look at this one, like it did in 2009?
We asked L3Harris whether any update or maintenance was done on FTI Friday.
We sent those questions to the FAA, Dayton International and L3Harris early Saturday. We'll add the answers when they come.
If you're flying this weekend, check your airline's app before you drive to Vandalia.
The secretary says it will fail again. He didn't say when.
Records for this story, including the Reddit timeline and the federal contract records, were gathered and sorted with AI tools. Rich Vandall reported, checked and edited it. The Despoiler uses Claude, an AI model made by Anthropic. Neither Anthropic nor any company named in this story has any role in our coverage.