The Federal Aviation Administration (FAA) has lifted a nationwide ground stop that halted departing flights across the United States for more than four hours after a “communication issue” affected air traffic control centres.
The FAA announced at 8:15pm Eastern time on Friday (01:15 GMT on Saturday) that it had lifted the order, after it issued the ground stop hours earlier at 3:54pm (20:54 GMT).
Airlines face delays and cancellations as they get aircraft and crews back into position.
The FAA said in a post on X in the afternoon that there had been a “temporary telecommunications outage” and that, as a precaution, all flights were being halted.
International flights would be handled case by case, it added.
More than 10,000 flights were delayed and over 4,000 cancelled, according to FlightAware, CBS News reported.
Some 4,042 flights were in the air, heading to US airports, when the ground stop was ordered, according to the tracking site Flightradar24.
The communication issue affected all 22 air route traffic control centres, which guide aircraft.
Homeland Security Secretary Markwayne Mullin told reporters there was no indication that the ground stop was triggered by a threat to the US.
“Everybody’s safe. The flights are accounted for,” he said. “This is not another 9/11.”
President Donald Trump had been briefed, he added.
Asked whether a planned rollout of a new AI tool meant to help air traffic controllers could be to blame, Mullin said officials have not ruled it out. “You just can’t rule out anything at this point. We are going through that process,” he said.
The FBI does not believe a cyberattack or criminal activity caused the failure, Bloomberg reported, citing an official familiar with the matter.
The cited official said investigators were examining whether a software update could have caused the outage, though the cause had not been determined.
Democratic Senator Tammy Duckworth has called for a “thorough and complete investigation” of the reported FAA communication issues.
“The safety of our skies is built on redundancies. Whatever led to the nationwide ground stop will warrant a thorough and complete investigation,” Duckworth wrote in a post on X.
“As Aviation Subcommittee Ranking Member, I’ll be demanding answers from the FAA,” she added.
The disruption is the latest sign of strain on the US air traffic control system, which has been beset by equipment failures, communications problems and shortages of controllers, as the FAA tries to replace ageing infrastructure.
Air Space Intelligence (ASI), the company behind the FAA’s AI-powered air traffic management system, said its technology was not responsible for the nationwide ground stop.
“The current ground stop is not based on or a result of the SMART system, any product of ASI or our integration with FAA and ATC,” the company said in a post on X.
The FAA awarded ASI an $875m contract in June to develop and deploy the SMART system, which uses artificial intelligence to support air traffic management.
The agency announced an expansion of the system across its 22 air traffic control centres on November 10, just days before the nationwide flight suspension.
US rail service affected
Amtrak, the US national rail operator, announced that its website and app are showing error messages and that customers are having difficulty reaching a representative, as it faces higher-than-normal call volumes because of the nationwide disruption to air travel.
“We apologize for the error messages on both our website and app, as well as the difficulty reaching a representative,” Amtrak said in a post on X in response to a complaint.
“We’re currently experiencing higher-than-normal call volumes due to ongoing airline issues,” the company said.
It recommended that customers try the services later.
Pilot and former FAA safety team representative Kyle Bailey told Al Jazeera: “Whether you are an expert or not, the bottom line is we’re still trying to piece the puzzle together, and it would be impossible to have an answer to the issue quickly, in a few hours at least.”
“But it is very alarming what we saw, and possibly [rail operator] Amtrak is being affected too,” he added. “The FAA’s priority at the moment is keeping not only the American passenger safe, but everyone flying in the US flight system.”
Bailey said that “halting the flights on the ground is the safest thing to do until they could figure out what’s going on. If anybody says they think they know what’s causing this problem at such an early stage, they’re not being honest”.
Congress approved $12.5bn for the overhaul last year, and the Department of Transportation and the White House asked lawmakers on Friday for another $30.1bn.
This was the first nationwide US ground stop since January 2023, when a key FAA computer system malfunctioned. Before that, the last time had been after the September 11, 2001, attacks.
US authorities have yet to determine the cause of the telecommunications outage that prompted the ground stop.
