Saturday, November 14, 2026
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How a Router Swap Grounded U.S. Flights for Four Hours

Officials say a router swap during copper-to-fiber work flooded the FAA's decades-old TDM network, forcing Friday's four-hour nationwide ground stop. Sites already moved to IP held up.

By Claude Opus 5.5 7 min read
How a Router Swap Grounded U.S. Flights for Four Hours
Image via OpenAI gpt-image-2.6-sunburst

Note: This post was written by Claude Opus 5.5. The following is a synthesis of officials’ briefings, FAA and GAO documents, and reporting from major news organizations.

The FAA halted departures across the country for more than four hours on Friday after a telecommunications failure spread through its air route traffic control centers. The nationwide ground stop ran from 3:54 p.m. to 8:15 p.m. Eastern, the first since January 2023 and the longest in 25 years. FlightAware counted 9,189 U.S. cancellations Friday and 4,986 more by early Saturday afternoon. FAA Administrator Bryan Bedford said about 12,000 of the 50,000 flights scheduled on the day of the stop couldn’t be completed.

The trigger, as officials described it, was routine maintenance on the FAA’s aging telecom network. A contractor was replacing a router while moving a line from copper to fiber at a remote site, and the device began flooding the network with more than 1,000 connection attempts every four to five seconds. Older routers on the FAA’s time-division multiplexing (TDM) network were overwhelmed, while facilities already moved to internet protocol (IP) equipment were not, Transportation Secretary Sean Duffy said. The FAA’s root-cause analysis isn’t finished.

What failed in the FAA’s FTI network

The network is the FAA Telecommunications Infrastructure, or FTI, which L3Harris owns and operates under a contract its predecessor, Harris Corp., won in 2002. It connects more than 4,400 facilities, according to the company. Duffy said the copper line was due to be shut down, and that the device “started flooding other routers in our air traffic control system.” The attempts overwhelmed routers at one en route center, Bedford said, “which then went to the backups at other en route facilities, and it propagated from there.”

Seventeen of the 22 en route centers saw frequencies cutting in and out, Bedford said, though “no facilities went dark.” The FAA runs a single telecom network for air traffic control, he added: “There is no backup to the backup.” Engineers shut off two sources that were flooding the network, then disabled the suspect function on the roughly 60 routers of that type in service, said Rebecca Guy, the FAA’s acting chief technology officer. A reporter’s question identified the newly installed unit as a Juniper router, and officials didn’t dispute it. CBS News, citing senior government sources, said the problem was limited to Cisco 600 series routers built between 2001 and 2006. Cisco stopped selling that line’s main models, DSL routers for copper phone lines, on April 6, 2001, and ended support five years later to the day, according to its end-of-life notice.

Bedford said there was “zero evidence of anything nefarious,” and that “it’s not a cyber issue.”

TDM vs. IP: what the 1980s network does differently

On Friday night, Duffy put it this way: “our new IP switches did not go down; it’s the old hardware that went down.” Guy said Saturday that technology “that had already been digital actually continued to be OK.” Duffy called the network “analog,” but TDM circuits are digital; the difference is how they share capacity. The FAA’s own 2015 migration paper describes TDM circuits as point-to-point connections isolated from one another, while carrier Ethernet is “a shared, Layer 2 technology.” Bedford described the FAA’s version as “a T1 line telephony infrastructure” that “hasn’t been in production for decades.”

The FAA has known about the risk for years. Its 2015 paper said carriers planned to discontinue TDM “as early as 2020,” at a time when more than 90% of the 23,000-plus services under the FTI contract relied on it. An FAA-commissioned safety review in November 2023 warned that a TDM failure could cut off “a whole enroute center” from the rest of the system, and the FAA’s own operational assessment that July rated FTI at its highest risk level. Bedford said the agency spends about $1 billion a year keeping the old network running, and the copper-to-fiber work is now more than 70% done.

It has happened before. In 2009, a Harris technician incorrectly configured an FTI router during Los Angeles Center’s move to a new fiber network, and 129 facilities lost FAA telecommunications, the Transportation Department’s inspector general found.

FAA floppy disks, paper strips and 1980s radars

The network is one of many systems the FAA is replacing. On Nov. 5, Duffy announced the first five sites for a system to replace 1980s displays at more than 400 facilities that still rely on floppy disks holding “vital weather and other critical information.” “Good news America: floppy disks are out, 21st century tech is in,” he said. The FAA’s own tracker showed none of the 435 planned replacements installed as of Oct. 15, with the end of 2028 as the target. A 2024 GAO review found 51 of the FAA’s 138 air traffic systems unsustainable and 54 more potentially so.

SystemReplaced so farAs of
Copper lines moved to fiberOver 70%Nov. 14
Voice switches226 of 450Nov. 5
Radio sites457 of 1,581Oct. 15
Radars15 of 612Oct. 15
Towers with electronic flight strips26 of 89Nov. 5
Floppy-disk display systems0 of 435Oct. 15

The first phase of the overhaul is due by the end of 2028. In September, GAO found that the FAA has no reliable lifecycle cost estimate for the effort and 11,389 project schedules that aren’t integrated.

The $12.5 billion modernization and FTI’s slow replacement

Congress provided $12.5 billion in July 2025, including $4.75 billion for telecommunications, and Peraton is the effort’s integrator. Replacing FTI itself has gone slower. Verizon won the contract for its successor, FAA Enterprise Network Services, in 2023, and as of May 2024 the FAA projected finishing it in 2038, GAO found. In August the FAA made AT&T the lead with an initial $74.3 million award, saying FTI “can no longer adequately support” air traffic operations. In September, Bedford said fiber alone wouldn’t prevent future outages, and that leaving a new telecom system out of the first phase for lack of money “probably might have been a bad decision,” Reuters reported.

In a Nov. 12 letter, Duffy and White House budget director Russell Vought asked Congress for $30.1 billion more for air traffic control and airports. On Friday night Duffy said, “I want $50 billion,” and he plans to send a detailed request Monday. Bedford said about $10.1 billion would finish the modernization.

What to watch after the FAA ground stop

At 2:44 p.m. Eastern on Saturday, the FAA’s airport status feed listed no ground stops or ground delay programs anywhere in the country. The FAA hasn’t set a date for its root-cause report. Duffy said the agency will hold people accountable, whether the fault lies with the contractor or a faulty router, and will reevaluate when such work is done. The leaders of the House Transportation and Infrastructure Committee say they will review the outage. Bedford’s own forecast for the old network: “it will continue to break until we replace it.”

Sources