Federal aviation officials were repeatedly warned that the push to rapidly modernize the nation’s air traffic control system risked breaking it, with the potential dangers spelled out in government reports in the months and years leading up to Friday’s nationwide ground stop that halted flights for nearly 4½ hours coast to coast.
A government watchdog report in September cautioned that the way the old, legacy systems were being replaced could result in disruptions — including ground stops.
A separate Federal Aviation Administration-commissioned safety review in 2023 also warned about potential air traffic disruptions from the agency’s technology updates, saying the FAA needed to ensure the old systems were preserved during the critical changeover period.
The predicted disruptions arrived Friday, resulting in more than 12,000 flight cancellations with outrage and delays rippling across the weekend.
Federal officials blamed a remote, overloaded router that a contractor was installing as part of a long-running effort to replace copper wires with fiber cables for air traffic communications nationwide. The router was sending “over 1,000 connection attempts every four to five seconds,” causing “instability” with the system that allows controllers to talk with planes cruising at high altitudes, Transportation Secretary Sean P. Duffy said Saturday.
Duffy painted it as an isolated incident, saying it was either a contractor’s error or faulty equipment. FAA Administrator Bryan Bedford said they needed to push ahead with the work. “It will continue to break until we replace it,” he said.
But the September report from the Government Accountability Office found that the FAA’s approach to delivering Duffy’s so-called Brand New Air Traffic Control System has prioritized “speed at the risk of cost uncertainty and potential disruptions.”
The effort involves more than 11,000 individual projects that GAO found were not being run with an overarching schedule. Individual facilities could have upgrades spread across multiple visits, GAO said, “without addressing potential conflicts, optimizing the schedules, or reducing disruptions to air traffic control operations.”
“Their approach could be a sound approach,” said an FAA technical official, speaking on the condition of anonymity because they were not authorized to discuss the project publicly. “The problem is it hasn’t been fleshed out.”
The official said the FAA’s approach carries risks because it involves making changes to a fragile, always-on system.
“Think about a car,” the official said. “I’m not just going to throw a new engine in there while it’s moving.”
In response to a question about why the work was carried out on a flight-heavy Friday afternoon, Duffy cited the urgency of the upgrades, which he said were being carried out in a remote location far from major flight corridors.
But, he said, “there will be a reevaluation of when we do this work.”
The FAA and the Transportation Department did not respond to requests for comment about the government reports warning of the risks of modernization efforts.
Aviation experts and federal officials agree on the need to update the aging technology behind the nation’s air traffic control systems. Efforts have been discussed for years, but action has been fitful.
Duffy made modernization a top agency goal when he took over under President Donald Trump last year.
Duffy has often touted the speed of the agency’s progress, while decrying the floppy disks, paper strips and antiquated computer parts still needed for controllers to safely guide planes through the nation’s airspace.
One air traffic controller, who spoke on the condition of anonymity because they were not authorized to speak with the media, confirmed that their co-workers sometimes need to source parts on eBay because the original manufacturer no longer makes it. That was the case with a recent piece needed for one control tower’s ground radar system.
“It was a two-week wait while we waited for the part to be delivered after it was ordered on eBay,” the controller said.
Last year, Duffy asked Congress for $31.5 billion to fund the Brand New Air Traffic Control System. He got $12.5 billion last summer to start.
Duffy said Saturday he wants to do far more than just replace copper wires with fiber cables. Among the items on his wish list: updating many of the nation’s aging flight control towers.
The copper-to-fiber switch appeared to pick up speed last year under a federal contractor, L3Harris Technologies.
Now, an estimated 70 percent of the work had been completed, Duffy said.
The U.S. firm is a major defense contractor and tech services provider that also happens to own the wired network serving, for the moment, as the air traffic control system’s nervous system.
Duffy, however, pointed the finger at L3Harris repeatedly on Saturday for the problems that led to the ground stop.
“We’re going to hold people accountable,” he said, adding: “Many of our contractors take our money and provide really poor service to us. Full stop.”
An L3Harris spokesman said it was supporting the FAA’s investigation “to understand the conditions that led to the Nov. 13 ground stop of our nation’s air travel.”
It was unclear following Saturday’s news conference with federal transportation officials why a single problematic router caused chaos across the country.
Tom Lintner, a former safety official at the FAA, said a disruption like Friday’s could recur if changes are not made.
“There’s a risk of this happening again, if they still try to push this modernization, which is necessary, on an unrealistic time frame,” Lintner said.
Lintner said he wanted to know whether the FAA conducted a safety case for the project, which would outline what could go wrong, the risks and how to mitigate them.
“They installed the receiver and it overpowered the system. That has a logical ring to me,” Lintner said. “The comeback question is: So you didn’t see this coming? And does that mean you experimented in trying to push this through because you’ve got this deadline at the next inauguration that you’ve got to get this done?”
“This has shades of the ballroom and arch,” he said, referring to other legacy-oriented projects by the Trump administration.
In November 2023, a group of aviation experts delivered a report on the safety of the nation’s airspace.
The report noted that the copper-wired communications backbone among facilities used technology so old that it is “no longer supported by the telephone companies’ lines on which the signals are actually carried.”
The FAA had continued to use the ancient system for budgetary reasons, and the agency knew it needed to move on. In July 2023, the FAA identified the Federal Telecommunications Infrastructure as among the highest-level risks to airspace safety.
But the experts’ report noted that moving to the proposed solution, set to take more than a decade to build out, also carried “the risk of losing communication with the rest of the (national air space) due to an unplanned failure.”
On Friday, that’s what happened.
A former senior official familiar with the experts’ report said there had been plans for the experts to examine other safety issues with the nation’s air traffic control system.
The FAA under President Joe Biden commissioned the group to launch a new inquiry in October 2024. The group’s first new meeting came shortly before Trump was inaugurated in January 2025.
But weeks after Trump took office, with new FAA officials in control, the group learned it was being disbanded.
No one seemed interested any longer in what they might discover, the former official said.
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