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Nov. 14, 2026

What Caused the FAA Ground Stop? Officials Point to an Overloaded, Decades-Old Network

What Caused the FAA Ground Stop? Officials Point to an Overloaded, Decades-Old Network

Photo: Federal Aviation Administration, public domain, via Wikimedia Commons.

What Caused the FAA Ground Stop? Officials Point to an Overloaded, Decades-Old Network

When we wrote about Friday's nationwide ground stop as it was happening, nobody official had said what broke. Now we have a first explanation from the people in charge, plus a few reported details that haven't been confirmed yet. Here's where it stands Saturday morning.

What officials said

At a White House briefing Friday night, Transportation Secretary Sean Duffy said routers and switches on the FAA's network got overloaded with data and started sending controllers inconsistent information. "Our routers actually got overloaded with data and … they started to give us inconsistency in the data from those routers. And because of that, we shut the system down," he said, according to CBS News.

Duffy put the problem on TDM, or time-division multiplexing, an older technology that still runs mostly over copper wire and carries air traffic control voice and radar data, the Los Angeles Times reported. "We have old, old switches, old routers, we use 1980s little copper lines," he said. He also said communications and radar were intermittent, not completely gone. But "when you have issues and you can't immediately communicate and immediately see where aircraft are at — that's a risk that we're unwilling to tolerate."

Homeland Security Secretary Markwayne Mullin pointed to a possible trigger. He said the FAA had been installing upgrades, and "that new equipment, new technology — it was overwhelming the older system."

Both officials said they had seen no evidence of a cyberattack. Mullin said the outage had nothing to do with this week's Microsoft outage, SecurityWeek reported, and officials said the FAA's new AI tools played no role. Mullin also said investigators are "still looking," so they aren't ruling anything out yet.

What's reported but not confirmed

CBS News, citing multiple sources, reported Friday that an update to the private communications network linking the air traffic control system caused the network to reboot and then crash. That network is the FAA Telecommunications Infrastructure, or FTI, and L3Harris runs it. L3Harris did not respond to requests for comment from CBS News or WIRED.

Bloomberg reported that the FBI doesn't believe a cyberattack or crime was behind the outage, and that investigators are looking at whether a software update caused it. That report cites one unnamed person familiar with the matter.

As of Saturday morning, the FAA has not announced an official root cause.

This wasn't a surprise

According to CBS News, the FAA first awarded the FTI contract to Harris Corp., the company that later became L3Harris, in July 2002. A November 2023 safety review commissioned by the FAA called the network obsolete and noted its reliance on TDM. WIRED reported that L3Harris said this month that 70% of FAA sites have been moved to fiber. WIRED also reported that the FAA picked AT&T in August to build the network that will replace FTI, with L3Harris running the old system until the switch is done.

That's the uncomfortable part. Rebuilding the system means working on it while it's still running live traffic, and Mullin's comments suggest that's exactly where this went wrong.

Why it matters from the cockpit

Pilots train for losing radio contact, and there are set procedures for it. Those procedures assume one airplane has a problem. They don't assume an entire en route center loses its picture or its frequencies at once. If controllers can't count on talking to airplanes or seeing them, you stop sending more airplanes into the system. That's the job a ground stop does. It's ugly for the schedule, but it was the right call.

The cleanup is still going. By Saturday morning, more than 3,200 U.S. flights had been cancelled for the day, per FlightAware data reported by The Washington Post. That's on top of about 9,000 on Friday, though weather caused some of those. Saturday is one of the lightest flying days of the week, so airlines are using it to get airplanes and crews back where they belong ahead of Thanksgiving. If you're flying this weekend, check your airline's app before you leave for the airport.

The bigger question is what the official cause turns out to be. If it really was an upgrade that took down the old network, the hard part of modernization isn't just the money. It's getting the cutover done without a repeat.

For more on how this looks from the other side of the radio, listen to our conversation with an air traffic controller: An Air Traffic Controller Tells All.

Sources

Aviation News

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