Major airlines on Saturday canceled more than 4,000 US flights and delayed 3,000 more as the United States sought to recover from the longest nationwide flight shutdown since the September 11, 2001, attacks.
The FAA on Friday issued a nationwide ground stop that halted nearly all departing flights for almost five hours due to a massive communications failure, which forced airlines to cancel nearly 10,000 flights and delay more than 7,000 others in one of the worst travel days in US history.
Transportation Secretary Sean Duffy said Saturday at a press conference that FAA contractor L3Harris was working at a remote location to convert copper to fiber.
Technology upgrades may have caused disruptions
"We're working to determine whether we had incompetence, meaning whether it was user error or installer error from L3Harris, or whether they installed a faulty router. We haven't determined what the fault was," Duffy said at a press conference.
The issue overloaded data at other communications centers. "We had over 1,000 connection attempts every four to five seconds, and what that did was give us issues with our communication with airplanes, and it also caused some disruption with our radar," Duffy added.
Delta Air Lines, United Airlines and American Airlines all canceled about 20% of their flights Saturday, while JetBlue canceled 40%.
Duffy said an AI scheduling tool or cyberattacks were not to blame.
Though the FAA eventually lifted the ground stop on Friday night around 8:15 p.m. ET, the disruption for passengers was far from over, with tens of thousands of people still stranded at airports around the country. Airlines were trying to clear airports and position flight crews and other personnel to recover from the massive disruption.
Many major airports said they could not handle any more diversions as they tried to get airplanes back in the sky. Many college football teams were stranded Friday and struggled to find ways to get to games Saturday.
Late Friday, American Airlines said it was prioritizing flights to international destinations and smaller cities outside its major hubs to position aircraft and crews for a faster recovery.
The FAA issued the ground stop because of an outage that appeared to affect a network that handles critical radio frequencies air traffic controllers use to communicate with pilots, according to two airline officials.
The contractor that oversees the network, L3Harris, did not respond to a request for comment.
Funds sought to fix 'emergency'
Friday's problem is the latest and most dramatic sign of strain on a US air traffic control system beset by aging technology, equipment and communications problems and a shortage of several thousand controllers.
Transportation Secretary Sean Duffy on Friday called for $50 billion to upgrade air traffic control systems, up from the $30 billion he had sought earlier. "This is an emergency," he said.
Duffy said the trouble began at 3:36 p.m. ET, when air traffic control centers experienced instability in radar and communications systems.
"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," Duffy said, adding that air traffic personnel never completely lost radar or communications as they guided thousands of planes to landings.
Duffy said the immediate problem was fixed and flying was safe, but warned that a broader overhaul of the air traffic control system was needed to prevent similar failures.
Earlier on Friday, before the outage, the White House and the Department of Transportation urged Congress to approve $30.1 billion to upgrade aging airports and air traffic control infrastructure.
"What we have is an incredibly old air traffic control system," Duffy said. "Give us the money to fix it."
Homeland Security Secretary Markwayne Mullin said there was "zero evidence" so far that the outage resulted from a cyberattack or a rogue AI system, though investigators had not ruled out either possibility.
The National Security Agency was working with the Department of Homeland Security on the investigation, he added.
Pain for passengers
From Boston to Seattle and New York to Los Angeles, passengers on Friday night crowded departure halls and airline desks as delays and cancellations mounted and aircraft remained parked at gates.
“I might cry at some point but not yet,” said Louise Maher, 47, who was stuck at Newark Liberty International Airport after the aviation meltdown disrupted her British Airways flight to London.
Because the FAA caused the delays, airlines are not required to compensate stranded passengers.
The only other nationwide ground stop since the September 11 attacks came in January 2023, when the FAA halted domestic departures for about 90 minutes.
Investors were already pricing in a financial hit to airlines. Shares of American, United, and Delta fell between 1% and 2% in after-hours trading late Friday, while JetBlue Airways dropped about 3%.
L3Harris shares traded down about 3% after hours.