WASHINGTON — The U.S. Department of Transportation was working Saturday to determine whether Friday’s air traffic control system meltdown resulted from human error or equipment failure as travelers across the nation continued to grapple with a cascade of flight delays and cancellations.

Transportation Secretary Sean Duffy said the crisis began when a contractor was performing routine maintenance at a remote FAA location to switch telecommunication lines from 1980s-era copper wire to a fiber line.

The new equipment began flooding other routers in the air traffic control system — sending more than 1,000 connection attempts every four to five seconds — causing radar and communications disruptions, he said. As a safety measure, the FAA decided to ground all planes for more than four hours.

It is unclear whether the contractor, L3Harris Technologies, or the piece of new equipment itself was at fault.

“This was an FAA system that didn’t meet the moment,” said Duffy. “A contractor didn’t meet the moment or the equipment didn’t meet the moment — and it caused the outages.”

A spokesperson for L3Harris said the company is supporting the FAA in its investigation to understand the conditions that led to the ground stop. L3Harris said safety and reliability are its highest priorities and that it takes the impact of Friday’s incident on travelers, airlines and air traffic operations seriously.

FAA Administrator Brian Bedford said he is hopeful airlines will be able to resume normal flight schedules by close of business Sunday.

There is no evidence that Friday’s system failure was caused by AI or any nefarious actors, Bedford said. He apologized to passengers impacted by the FAA’s decision to ground flights and emphasized that no lives were harmed during the crisis.

“I’m sorry that we put you through this, but we did it for the right reasons,” he said.

Duffy said the ground stop highlighted the need to continue modernizing the FAA’s “incredibly old” telecommunication system. Currently, around 70% of the system has been moved to a fiber network, but the remainder relies on copper wire, he said.

Duffy thanked President Donald Trump for securing a $12.5 billion investment in the FAA through his 2025 “Big Beautiful Bill” and called on Congress to approve an additional $30 billion funding request to continue modernizing the nation’s aviation infrastructure.

Chaos reigns at airports across America

On Saturday morning, thousands of planes were back in American airspace, but airlines warned it would take several days to recover and urged passengers to change their flights to later dates where possible. The FAA anticipates that 4,000 to 5,000 of the 41,000 flights scheduled in America on Saturday will be canceled, Bedford said.

On Friday, there were more than 7,400 flight delays within, into, or out of the United States and more than 9,000 cancellations, according to flight-tracking website FlightAware.

Leis Rodriguez’s flight from LAX to San Antonio at 6:30 p.m. Friday was among the thousands that were grounded. She and her sister were rebooked for a Saturday morning flight, but it was delayed, leaving them to sit for hours in the airport hoping they’d be able to board at some point.

“We have to rely on a lot of patience,” Rodriguez said. “Not knowing if your flight is going to be canceled is anxiety-producing.”

Despite the inconvenience and uncertainty, she’s glad the government took action and grounded flights on Friday.

“Safety is paramount, and I’d rather have this experience than have any kind of huge safety risk,” she said.

Sister Nyla Butler and Elder Zachary Woods, both missionaries with the Church of Jesus Christ of Latter-day Saints, were on the tarmac Friday in Melbourne when they got word of flights being grounded in the U.S. They eventually made it to LAX, but missed their connecting flights home to Alberta and Seattle, respectively.

On Saturday morning, the 20-year-olds wore their church name tags as they stood with their luggage in a line of hundreds of people hoping to rebook flights.

“There’s just been a lot of confusion, having no idea where we are, what line we’re supposed to be in,” Woods said.

Vivi Zhang, meanwhile, sat despondently with her luggage on a windowsill near a lengthy check-in line. Her 7 a.m. flight to Calgary was canceled, and the next available flight is Sunday. She said she was frustrated by the lack of support from airline staff.

“No food, no hotel voucher, anything,” she said. “They just said ‘not our fault.’”

Democrats outraged over handling of crisis

The ground stop sparked barbed political discourse over the initial lack of clear communication from White House officials and how a routine upgrade could generate such a disastrous impact on the FAA’s watch.

“The Transportation and Homeland Security leaders were slow to provide updates, and when they did speak, they didn’t have good explanations about what was happening, nor whether it would happen again,” Rep. George Whitesides, D-Calif., said in a Friday evening statement on X.

Whitesides, who was himself stuck in an airport for seven hours Friday, criticized the president for installing a Transportation Secretary with “basically no professional transportation experience in one of the most crucial jobs we have as a country.” Duffy is a former sports television personality, prosecutor, congressmember and CNN political contributor.

New York Gov. Kathy Hochul called on Duffy to resign or Trump to remove him from his post.

“From chronic air traffic controller shortages to repeated communications breakdowns, serious lapses in our aviation system have become a pattern on Sean Duffy’s watch,” she said in a statement Saturday. “Through it all, he’s been more focused on starring in his own reality show than addressing the crisis at his agency.”

Former Transportation Secretary Pete Buttigieg questioned why an isolated equipment failure resulted in such a sustained disruption of the nation’s air traffic control system.

“The system has many redundancies in it so that normally, if there’s one point of failure, something else can catch it,” he said Friday, noting that when a system crashed under his tenure as secretary in 2023 the outage was shorter, lasting around 90 minutes.

“There were actually four different systems, and one of them went out, and another one could be brought online to cover,” he explained, “so it is not clear to me why that redundancy did not prevent an outage of this magnitude in terms of the scope and duration.”

Trump, who rarely shies away from the spotlight, did not comment on the unprecedented telecommunications outage Friday. When asked about the president’s silence at a Friday evening news conference, Duffy said that Trump was “fully engaged” behind the scenes.

On Saturday, Trump posted a quote from Sen. John Kennedy, R-La., on Truth Social that detailed the legislator’s political priorities, including getting Democrats’ support on a FAA funding bill.

Earlier in the day, Duffy called on Democrats and Republicans to unite and approve funding to finish modernizing the FAA’s air traffic control network and upgrade other aging infrastructure, such as towers and tarmac, at airports across America.

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(Times staff writer Ana Ceballos contributed to this report.)

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