A communications failure across the US air traffic control network triggered the country’s longest nationwide aviation shutdown since the September 11 attacks, disrupting thousands of flights and exposing the risks posed by infrastructure that federal authorities have struggled for years to replace.
The Federal Aviation Administration ordered a nationwide ground stop on Friday afternoon after a failure affected all Air Route Traffic Control Centers, preventing aircraft from departing airports across the United States. The shutdown lasted more than four hours, but its effects continued into Saturday as airlines worked to reposition aircraft, restore crew schedules and clear a backlog of stranded passengers.
More than 3,000 US flights had been cancelled and nearly 1,000 delayed by 5:45 a.m. ET on Saturday, according to flight-tracking service FlightAware. That followed approximately 9,000 cancellations and more than 7,000 delays on Friday, although some of the disruption was also caused by adverse weather.
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The scale of the disruption placed pressure on airlines as they attempted to restore operations ahead of the Thanksgiving travel period. Saturday is typically one of the lightest days for airline schedules, giving carriers an opportunity to deploy spare aircraft and crews to recover from the shutdown. Aviation data firm Cirium estimated that around three million passengers would normally be scheduled to fly on Saturday.
Transportation Secretary Sean Duffy said the outage was caused by overloaded switches and routers in the FAA’s legacy communications network, which began transmitting inconsistent information to air traffic control centers.
The equipment problem reportedly began at 3:36 p.m. ET. Officials said technicians were investigating the failure, although the precise cause of the overload had not been established.
President Donald Trump blamed the disruption on what he described as a “bunch of old broken stuff” in the country’s air traffic control infrastructure. Duffy also criticized Congress for delaying funding needed to modernize the system, warning that similar failures could occur again without a comprehensive upgrade.
The administration said there was no indication that the incident was caused by a cyberattack.
The FAA said it had tested its systems before allowing flights to resume. “Before clearing flights to resume, we thoroughly tested our systems to confirm they were stable and that operations remain reliable,” the agency said late Friday.
The shutdown has renewed scrutiny of an air traffic control network that has been the subject of repeated warnings from government auditors and aviation officials.
The United States operates the world’s busiest airspace, relying on a complex network of radar systems, telecommunications equipment and computer infrastructure to coordinate aircraft movements between airports and control centers. Much of that equipment is ageing, while different facilities continue to depend on systems that do not communicate seamlessly.
A 2024 report by the Government Accountability Office found that the FAA had classified 51 of its 138 air traffic control systems as unsustainable and another 54 as potentially unsustainable. Together, the systems accounted for more than three-quarters of those reviewed.
FAA Administrator Bryan Bedford told Reuters in September that more than 300 air traffic facilities operated as technological silos, with some still relying on decades-old computers and telecommunications systems. Certain obsolete components have become so difficult to obtain that replacement parts must sometimes be sourced through online auction websites or produced using 3D printing.
Friday’s failure demonstrated how a problem in the communications network can quickly affect the entire aviation system. Air traffic controllers depend on reliable data exchanges between facilities to coordinate flights safely. When that information becomes inconsistent or unavailable, authorities may have to restrict departures to maintain operational safety.
The incident was not the first recent example of weaknesses in the network. In September, a telecommunications circuit serving a Philadelphia air traffic control facility developed errors. The FAA’s contractor switched operations to a backup fiber-optic line, but a construction crew subsequently severed that line in New Jersey, contributing to widespread disruption. About 9,500 US flights were delayed or cancelled that day.
“When it fails, we just don’t have the redundancy that we would get if we had a modern architecture,” Bedford said at the time.
The episode highlighted a problem that extends beyond the age of individual components: the limited ability of the existing network to maintain operations when primary and backup systems fail.
Friday’s shutdown was the first nationwide ground stop since January 2023, when a failure in the FAA system responsible for distributing critical safety notices to pilots halted departures for less than two hours and disrupted more than 10,000 flights.
Challenges of Modernization
The latest outage occurred on the same day the White House and Transportation Department sought another $30.1 billion from Congress for airport and air traffic control improvements. The request included $10.1 billion for modernizing air traffic control infrastructure.
Congress had already approved $12.5 billion in July 2025 for upgrades to the country’s ageing system, including telecommunications and radar equipment. The administration said on Friday that 68% of the FAA’s legacy copper telecommunications network had been replaced with high-speed fiber.
However, Bedford has warned that replacing copper wires with fiber-optic cables alone will not resolve the system’s underlying weaknesses. The agency needs a modern telecommunications architecture capable of connecting facilities reliably and providing adequate backup capacity when individual components fail.
The modernization programme also faces significant planning problems. In September, the GAO warned that the FAA lacked a reliable cost estimate and an integrated master schedule for the overhaul.
As of May, the agency had 11,389 separate project schedules that were not coordinated. The watchdog warned that this fragmented approach could lead to duplicated work, delays and cost overruns, complicating efforts to replace outdated infrastructure within the planned timeframe.
The FAA aims to complete the first phase of the modernization programme by December 2028. But the GAO cautioned that inadequate planning increased the risk of delays, potentially leaving the agency dependent on vulnerable legacy systems for longer.
Duffy said the shutdown would take time to unwind, even after the FAA restored departures. Aircraft had been diverted to alternative airports, crews were displaced from their planned schedules, and passengers were left waiting for replacement flights.
“I believe that it’s going to take us some time to get back to capacity,” he said on Friday night. “We’re going to have some makeup to do.”
He also warned lawmakers that continued delays in approving infrastructure funding could leave the country exposed to further disruptions.
The immediate priority for airlines is to restore schedules and move passengers before the Thanksgiving travel rush. But the wider challenge is more difficult. The shutdown showed that the reliability of US air travel depends not only on aircraft, airport capacity and airline operations, but also on the communications infrastructure connecting hundreds of air traffic facilities.