The FAA Grounded Every Flight in America, Explained

Friday afternoon, the FAA told every plane in America to stay put. Not one airport, not one region — the whole country, all at once, for more than four hours. If you were flying today, you already know. If you weren't, here's what happened, what we know about why, and what's still just a rumor.

What happened

Just before 4 p.m. Eastern on Friday, November 13, the FAA's Air Traffic Control System Command Center issued an order nobody had seen in years: every airport in the United States was ground stopped. All departing traffic was to stay put until further notice. The advisory's own words were stark — "due to extraordinary circumstances and for reasons of safety."

Here's what that actually meant. No plane could take off, anywhere in the country. Planes already in the air kept flying and landed as normal — this was departures only. International flights coming in were handled case by case. And by around 5:45 p.m., some international departures from the east and west coasts were getting the go-ahead again.

The stop lasted just over four hours. The FAA lifted it around 8:15 p.m. Eastern, and departures started moving again. But four hours of nothing taking off doesn't just end when the order lifts — crews and planes were in the wrong places, and the knock-on effects were still piling up late into the night.

So what caused it?

Start with what the FAA itself said. Its statement, published Friday, is short: the ground stop followed "communication issues impacting multiple Air Route Traffic Control Centers," and its technicians were investigating. In a separate post, the agency called it "a temporary telecommunications outage" and said every flight had been accounted for.

Transportation Secretary Sean Duffy filled in more at a White House briefing that evening. At 3:36 p.m., he said, the system started showing "instability for our radar and our communications" in the centers and the TRACONs — the facilities that guide planes between airports and around busy airspace. The switches and routers, he said, "got overloaded with data" and started giving inconsistent readings. Faced with data it couldn't trust, the agency shut the system down. Duffy's shorthand for the cause: a "legacy network." Old switches, old routers, too much data.

That's the confirmed part: a technology failure, not weather, not a threat. Now the reported part. CBS News, citing multiple sources, reported that an update to the private communications network linking the air traffic control system caused it to reboot — and then crash. The Wall Street Journal reported the outage "appears to involve" the network run by defense contractor L3Harris, which has operated the FAA's telecommunications backbone for more than twenty years. L3Harris didn't immediately respond to requests for comment. Treat that as reported, not confirmed: the FAA has not named L3Harris or an update as the trigger.

And the rumors. Two worth clearing up. First, no, this wasn't a cyberattack — at least, nothing so far points that way. Homeland Security Secretary Markwayne Mullin said there was "no indication" of one, the FBI doesn't believe so either, according to reporting, and Mullin added there was "no evidence of a cyber-attack or artificial intelligence attack." He also said, honestly, that "there's not complete certainty right now" — the investigation is still going. Second, no, it wasn't the AI tool, either. Three days before the outage, the FAA had rolled out an AI system called SMART to all 22 centers. The FAA and the company behind it both say it played no role — and if the jargon is new, our What Is AI? page explains what these systems are. And it wasn't NOTAM, the system that failed in January 2023 — that was a different outage, a different cause. Nobody has tied NOTAM to this one.

So where does that leave us? The technology failed — that's confirmed. Which exact piece failed first, and whether it was a bad update, an overloaded router, or something else entirely — that's still the open question.

FlightAware's Friday tally, via reporting. Counts were still moving late Friday night.

If you're flying

The stop is over, but your flight might not be fine yet. JetBlue canceled its remaining Friday flights. Air Canada canceled all its flights to and from the US for the rest of the evening. Around 800 Saturday cancellations were already on the board by Friday night. Crews and planes are out of position, and it takes a while to unwind that.

If you're flying this weekend, check your flight status before you leave for the airport — and expect rebooking lines and full flights while the system catches up. Duffy said he expects flights to be "back up and operational" heading into Thanksgiving, which is less than two weeks away. That's the test now: whether the recovery holds before the busiest travel week of the year.

And a bit of context for how rare this is: the last time the FAA halted all departures nationwide was January 2023, when a failed computer system did it for about 90 minutes. Today's stop lasted roughly three times as long — and it was only the second nationwide halt of all departures since the September 11 attacks.

What we still don't know

The big one: the exact trigger. The FAA's statement calls it a communications outage and says technicians are investigating. Duffy blames overloaded legacy hardware. Reporting points at an update on the L3Harris network. Those three things might all be true at once — an update overwhelming old routers on a legacy network — but nobody has confirmed the full chain yet, and the FAA's own statement is marked "preliminary and subject to change."

We also don't know yet whether anything will change because of it. The network at the center of this — the FAA Telecommunications Infrastructure — has been running for more than twenty years and is in the middle of a multi-year modernization, copper wire being replaced with fiber. AT&T was brought in this August to rebuild it, with the new system due in December 2028. Whether this outage speeds that up, or changes anything else, is a question for the weeks ahead.

The honest summary: a technology failure stopped every departing flight in America for four hours. Nobody was hurt, nothing was attacked as far as anyone can tell, and the planes are moving again. The part that matters now is the recovery — and the answer to a question the FAA hasn't given yet: what, exactly, broke.

Sources & further reading

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