The Federal Aviation Administration lifted a rare nationwide ground stop Friday evening after a telecommunications problem disrupted air traffic control centers and halted departures at airports across the country for roughly four hours.
The FAA’s order was lifted at about 5:30 p.m., but widespread delays and cancellations were expected to continue affecting travelers.
U.S. Transportation Secretary Sean Duffy said Friday night that aging air traffic control equipment and data-overloaded routers triggered the disruption.
“What we have is an incredibly old air traffic control system,” Duffy said at a news conference. “Our routers actually got overloaded with data.”
Duffy said the routers began providing inconsistent data, prompting the FAA to shut down the system as a safety precaution. He said some routers had been replaced, but older hardware failed.
The FAA issued the nationwide ground stop shortly after 1 p.m. Friday because of a communications issue affecting all 22 Air Route Traffic Control Centers, including the center in Palmdale.
The order required all departing aircraft to remain on the ground while technicians investigated the problem. Flights already in the air continued to land, while inbound international flights were to be handled on a case-by-case basis.
Duffy confirmed the order in a post on X shortly after 1 p.m.
“The FAA issued a nationwide ground stop for all U.S. airports following a communication issue impacting all Air Route Traffic Control Centers,” Duffy wrote. “FAA technicians are investigating the issue.”
An alert sent to airports nationwide and shared online by the flight-tracking site Flightradar24 said the stop was issued “due to extraordinary circumstances and for reasons of safety.” The alert stated that all traffic should remain ground stopped until further notice.
Los Angeles International Airport officials advised passengers on X that the order was affecting departing flights from LAX.
“Please anticipate delays and contact your airline for flight status,” LAX officials said.
Ontario International Airport said it was monitoring the situation and urged passengers to check with their airlines for updated flight information.
FlightAware, a flight-tracking website, reported more than 9,500 flight delays and about 5,300 cancellations nationwide by Friday evening. At LAX, more than 600 flights were delayed and more than 280 were canceled, according to FlightAware.
Homeland Security Secretary Markwayne Mullin said the disruption was a telecommunications outage and not a national security threat.
“There is no reason for the public to be afraid or scared for their loved ones,” Mullin said Friday afternoon.
Mullin said there was no indication the outage was the result of a cyberattack or other “nefarious act.”
According to various reports, localized ground stops were issued at Chicago O’Hare and Midway international airports shortly before the nationwide order because of an equipment outage. It was not immediately clear if the incidents were related.
Yahoo News reported that one of its reporters was aboard a United Airlines flight waiting to depart from LAX when the pilot said the communications issue began at an air traffic control center in Kansas City before spreading nationwide.
The outage occurred one day after the FAA announced an expansion of an artificial intelligence-based flight-management system known as SMART, or Strategic Management of Airspace, Routes and Trajectories.
The system, initially used in the Washington, D.C., area, was being expanded to all 22 air traffic control centers to reduce delays, cut fuel consumption and improve the travel experience, according to the FAA.
It was not immediately clear whether the SMART expansion was connected to Friday’s communications problem. Mullin said an investigation would determine whether the system played any role.
Air Space Intelligence, the company that developed and operates the SMART system, said in a post on X that the ground stop was not connected to its technology.
“The current ground stop is not based on or a result of the SMART system, or any product of ASI or our integration with FAA and ATC,” the company said.
The disruption marked only the second nationwide FAA ground stop since the Sept. 11, 2001, terrorist attacks. The last one occurred in 2023, when a pilot notification system failed.