FAA ground stop: the air traffic network that failed is one the FAA said in August could no longer cope

Latest developments

• 14 November, 08:30 EAT: US airspace reopened at 8:15pm Eastern on 13 November (04:15 EAT, 14 November) after a ground stop of more than four hours. Officials have not yet said publicly which update or piece of equipment failed first. L3Harris, which runs the network, had not commented by the time of publication.

Analysis

For more than four hours on Friday 13 November, no commercial departure left an American airport without special clearance. The Federal Aviation Administration (FAA) halted departures nationwide shortly before 4pm Eastern time after radar and communications at its en-route control centres became unstable from 3:36pm. Chicago O’Hare and Midway had been stopped from 3:10pm. Transportation Secretary Sean Duffy reopened the airspace at 8:15pm. It was the longest nationwide shutdown since the attacks of 11 September 2001, Reuters reported, and only the second nationwide ground stop since then. The first, in January 2023, followed the failure of the system that sends safety notices to pilots.

By Friday night FlightRadar24 counted more than 6,600 cancellations and 8,600 delays, according to Reuters. FlightAware had recorded more than 6,000 cancellations by 9pm. Mr Duffy said about 3,500 aircraft were airborne when the stop began. All of them were accounted for, and Homeland Security Secretary Markwayne Mullin said there was “zero evidence” so far of a cyberattack, though investigators had not ruled one out.

Officials quickly settled on one explanation: the system is old. “Our switches, our routers actually got overloaded with data and they started to give us inconsistencies in the data from those routers, and because of that we shut the system down,” Mr Duffy said. He then asked Congress for $50bn. That account is true as far as it goes. What it leaves out is that the network did not simply wear out. By officials’ own description it broke while it was being replaced, and the FAA had already said in writing that it could no longer cope.

What failed

The network at the centre of the outage is the FAA Telecommunications Infrastructure, known as FTI. It is the private backbone that carries controllers’ voice links and radar data between FAA facilities. The FAA gave Harris Corp., now L3Harris Technologies, the contract to run and modernise it in July 2002. L3Harris says FTI connects more than 4,400 facilities and supports 45,000 flights a day. Two airline officials told Reuters the outage hit a network overseen by L3Harris. CBS News, citing several sources, reported that an update to the network made it reboot and then crash. Mr Mullin said new equipment and security patches put into the older system appeared to have “overwhelmed” its routers. The FAA has not yet said publicly which update or component failed first, and L3Harris had not responded to requests for comment from Reuters, CBS or Wired.

That matters because FTI is in the middle of a rebuild. L3Harris is moving FAA sites from copper lines and time-division multiplexing (TDM), a telephone-era way of carrying signals, to fibre, satellite and wireless links. On 2 November its website said 70% of sites had been upgraded. Its pitch for the work promises that its “deep knowledge of the U.S. national airspace allows us to upgrade systems without disrupting air traffic operations”. If officials’ preliminary account holds, the failure came from the meeting point between old and new equipment, which is exactly where a migration carries the most risk.

The FAA’s own paper trail

None of this was hidden. In November 2023 an FAA-commissioned safety review team called FTI “obsolete”. It said the network ran on TDM technology “no longer supported by the telephone companies’ lines on which the signals are actually carried”. It warned that until a replacement was fully built, a facility, “possibly a whole enroute center”, could lose contact with the rest of the airspace system after an unplanned failure. The FAA’s July 2023 operational risk assessment had already put FTI risk “at the highest level”, the review noted. It also described a bridging solution from the incumbent contractor to keep old and new technology compatible, and said it was “very expensive”.

The replacement programme, FAA Enterprise Network Services (FENS), has been slow. Verizon won it in March 2023 as a 15-year programme. On 11 August 2026 the FAA moved the prime role to AT&T, without competition, using waiver authority granted for the Brand New Air Traffic Control System. Verizon moved to a supporting role. The initial AT&T task order is worth $74.3m, and the FAA expects a multibillion-dollar contract once terms are final. In its public justification for the award, posted on the federal contracting site SAM.gov, the FAA said: “The current FAA Telecommunications Infrastructure network can no longer adequately support NAS operations or BNATCS requirements.” It said a competitive tender would take at least 22 months and make its December 2028 deadline for the new system “impossible to meet”.

Put plainly, three months before the outage, the agency told the market that the network carrying America’s air traffic could not do the job. It also set out a plan under which that same network has to keep working until at least late 2028.

Who holds the power, and who answers for it

The rebuild is split across contractors. L3Harris runs the legacy FTI network and its copper-to-fibre replacement. AT&T is planning and designing the FENS network that is supposed to succeed FTI. Peraton was picked in December 2025 as prime integrator for the wider air traffic control overhaul, according to Washington Technology. The FAA sits on top as buyer, operator and regulator of its own system. When a failure happens at the join between two generations of equipment, that split makes it harder to say who was responsible. That is why the root-cause findings the FAA has not yet published matter more than the funding numbers. They will show whether this was a failure of age, of change management during the migration, or of contract oversight.

Congress holds the money, and it has questions of its own. Lawmakers approved $12.5bn in July 2025 for air traffic control upgrades and controller hiring, including $1.9bn to replace en-route centres, AeroTime reported. On Friday morning, before the outage began, Mr Duffy and White House budget director Russell Vought asked Congress for $30.1bn more: $10.1bn for air traffic control modernisation, $2bn for towers and $18bn for airport projects, $10bn of it for terminals. That evening Mr Duffy asked for $50bn and did not explain how the two figures related. Mr Mullin called $50bn the estimated cost of “a complete overhaul”. In September Senator Jerry Moran, the Republican who chairs the Senate aviation subcommittee, said he backed more funding but wanted to know how the FAA had spent the money already approved.

Most of Friday morning’s request was for airports and terminals, not the communications backbone that failed. A bigger cheque does not by itself shorten the period when FTI and its replacement have to run side by side. That overlap is the window of risk the 2023 review described.

Who bears the burden

Passengers bore the immediate cost. Mr Duffy said tens of thousands were stranded. Reuters reported that US airlines are not required to compensate them, because the failure was the FAA’s, not the carriers’. Airlines absorb the cost of repositioning aircraft and crews. Shares in American, United and Delta fell 1% to 2% in after-hours trading and JetBlue dropped about 3%, Reuters said. JetBlue cancelled its remaining Friday flights except some Europe-bound departures. Freight and mail flights were also affected, Wired reported.

The disruption also crossed borders. Reuters spoke to a passenger in Newark whose British Airways flight to London was caught up, and to a Pennsylvania resident booked on an evening Ethiopian Airlines flight to Lomé, Togo, who planned to sleep at the airport before a rebooked 6am departure. Foreign carriers depend on American air traffic control as much as US ones do, and have no say in how it is run or paid for.

What happens next

Several things are now in motion. Senator Maria Cantwell, the ranking Democrat on the Senate Commerce Committee, said the committee was looking into the telecommunications failure. The committee’s Republican majority said the outage showed why the FAA should give the en-route centres priority. The first test is whether the FAA publishes a clear root cause: which update, which equipment, whose change process. Without one, the debate stays at the level of “old routers”.

Then there is the calendar. Democrats won both chambers in the 3 November midterms and take their majorities in January 2027. The administration can try to get emergency money through the lame-duck Congress or make its case again to Democratic committee chairs next year. President Donald Trump has said he will work with the incoming Congress. Mr Duffy said he expected operations to recover before the Thanksgiving rush. Asked whether the failure could happen again, he said he could give no guarantee.

The most likely near-term path is hearings and a funding fight, while the network itself carries on largely as before. The copper-to-fibre work continues, FENS stays in its planning phase and the 2028 target stands. A less likely, but possible, outcome is that investigators find a specific failure in how changes were tested and deployed on FTI. That would move the argument from how much to spend to how the migration is run, and would test whether splitting the work across L3Harris, AT&T and Peraton leaves anyone clearly responsible.

The lesson of 13 November is not just that America’s air traffic system is old. Officials say it failed while being modernised, after the agency had warned in public documents that its backbone could no longer cope. The risk does not end when Congress approves the money. It ends when the old network can be switched off, and on the FAA’s own timetable that is still at least two years away.

What we know and don’t know

• Established: the timeline of the ground stop; the FTI network’s role; the contents of the 2023 review and the August 2026 FAA contract justification; the funding requests.
• Attributed and preliminary: that an update or patch on the L3Harris-run network triggered the failure (officials and unnamed sources cited by CBS and Reuters); that there was no cyberattack (DHS, investigation continuing).
• Unknown: which component or change failed first, and who authorised it.