One Router Swap Grounded U.S. Flights. The Rest of the Fleet Was Due in 2006.

A contractor’s copper-to-fiber work at one remote site flooded the network that carries voice and radar data, and the Federal Aviation Administration stopped every departure in the country for four hours and 21 minutes. Whether the fault lies with the new unit or the 25-year-old fleet it was replacing, the agency’s own review in 2023 had already called that network obsolete.

On Friday, Nov. 13, 2026, at 3:54 p.m. (UTC-5), the Federal Aviation Administration (FAA) stopped every departure at every airport in the United States. The order held until 8:15 p.m., four hours and 21 minutes, the longest nationwide ground stop since the attacks of Sept. 11, 2001, and the agency’s first statement named no cause: communication problems at multiple Air Route Traffic Control Centers, technicians investigating, information preliminary.

More than 15,000 flights were delayed or canceled in the country, by the British Broadcasting Corporation (BBC)’s count of tracking data, affecting an estimated 1.5 million passengers. Aircraft bound for the United States were held on the ground in Europe and in Australia, and some passengers spent hours inside parked planes unable to return to a gate, and the disruption was still spreading into Saturday.

The escalation the controllers saw

Bryan Bedford, the FAA administrator, said the agency received reports from 17 of its 22 en route centers, the facilities that sequence aircraft between airports and hold them apart in cruise, and that none of them “actually went dark,” as Cable News Network (CNN) reported. Controllers reported radio frequencies fading in and out and switched between primary and backup systems.

“If that had been a single facility, we would have just worked through it,” Bedford said. “But when we saw it go to two, three, 10, 17 facilities, that’s when we started to realize there was something much larger going on here.” With no root cause in hand and the fault still spreading, the agency closed the airspace.

A router, a remote site and over 1,000 attempts every four to five seconds

The explanation came on Saturday, Nov. 14, 2026, when Sean Duffy, the transportation secretary, and Bedford held a briefing at the Transportation Department, whose transcript records the sequence in their own words. In at least one remote FAA location, Duffy said, a contractor was carrying out routine maintenance to move telecommunications lines from copper wire to fiber, the old copper having reached the point where its supplier was discontinuing it. The contractor was L3Harris, which he described as the agency’s legacy provider of more than 20 years and the owner of the network the FAA uses to control the airspace.

As that router was being replaced, Duffy said, it began flooding other routers in the system with “over 1,000 connection attempts every four to five seconds,” which degraded communication with aircraft and disrupted radar feeds. When crews isolated the work at the remote site, he said, the systems returned and the airspace reopened. He ruled out an attack: “We don’t believe this was cyber at all.” Bedford said the agency had zero evidence of anything “nefarious” and zero evidence of anything related to artificial intelligence.

What failed is still in dispute

Duffy said the agency was trying to establish whether L3Harris had made a mistake in the installation or installed a defective router, and that it would “hold people accountable.” Reuters reported that routers installed in Arkansas and in Texas may have been involved, and that the equipment being swapped out was about 25 years old and had been scheduled for replacement in 2006.

A different group of senior government sources said the failure was limited to Cisco 600-series routers built between 2001 and 2006, which buckled under the load and began feeding out-of-sync data packets into the wider system, producing static on voice circuits and screens that flashed or went black. Those same sources said the equipment had been identified and isolated, and that they were themselves receiving conflicting accounts of what happened.

The two versions point at opposite sides of the same swap. Duffy described the unit going in as the one that flooded the network; the CBS News account described the routers coming out as the ones that broke. Either way, the equipment sat on lines of the same vintage, in a fleet that had been scheduled for replacement in 2006.

The hours the sky was closed

During the closure the FAA had two jobs: land the aircraft already in the air and find the fault. Duffy said 3,500 aircraft were in the air when the order went out and that controllers and pilots landed all of them without incident. Once the maintenance at the remote site was halted and the systems stabilized, the agency tested the network before clearing departures, and more than 8,000 operations resumed that night alone, he said.

Duffy later said the FAA system “didn’t meet the moment.” Bedford framed the episode as an old technology behaving as predicted: the equipment is old, the agency knows it, and it will keep breaking until it is replaced.

The network the FAA does not own

The FAA Telecommunications Infrastructure (FTI) is the backbone that carries voice and operational data between control centers and other agency facilities. Harris Corp., the predecessor of L3Harris, won the contract to modernize, operate and manage it in July 2002. The ownership question surfaced at the briefing, when Duffy was asked what the contractor had done.

They own this network. They’re our prime contractor. I can’t go somewhere else. They own it.

The money has arrived in pieces. The agency spends $1 billion a year maintaining the network it is trying to retire, according to Reuters, and Bedford put the same figure on sustaining what he called the FAA’s 1980s telephone system. He described an ongoing program that swaps a fleet of 2,000 Cisco 600 routers for Juniper equipment, work he separated from the $12.5 billion modernization program, which he attributed to another contractor, Peraton. Duffy, in the same briefing, presented the copper conversion as the record of what that money had bought: 69% of the copper moved to fiber, about 30% still to go and the agency still working out where the remaining lines are. L3Harris says it has completed more than 70% of the conversion and is supporting the investigation.

In November 2023, a safety review commissioned by the agency described the FTI network as obsolete, dependent on a transmission technology that telecommunications carriers no longer support, and warned that an unexpected failure could disconnect an individual facility or an entire regional control center from the rest of the network. Friday’s failure took the shape the review described. Duffy asked Congress for money within hours of reopening the sky, and Mike Johnson, the outgoing House speaker, said Republicans would use the remaining 50 days of their majority to authorize more spending on the agency.

A familiar kind of failure

Small faults have repeatedly reached the whole system. Reuters, in its account of the weekend, reported a ground stop in January 2023 set off by a contractor that deleted files by accident, lasting 90 minutes and disrupting 11,000 flights, along with failures caused by errant fiber cuts and by a melted component that filled a room with a chemical smell. Reuters also reported that in September 2026, a circuit failure at a facility in Philadelphia and a fiber cable severed by a construction crew in New Jersey delayed or canceled thousands of flights across the Northeast.

The pattern explains the size of the outage. A network assembled from a 2002 operating contract, a copper retirement at 69%, a router fleet past its scheduled replacement and a modernization effort split between at least two contractors produces failures of exactly this size: one unit, one small change at a remote site, hours of closed airspace. The FAA is investigating a failure inside a network owned by the company it pays to run it. The maintenance that grounded the country was part of a replacement scheduled for 2006 and still unfinished, and the upkeep of the equipment still in place is billed every year in full.