A person looks at a departures board showing delays and cancellations at LaGuardia airport on Friday in the Queens borough of New York City. Adam Gray/Getty Images hide caption

Adam Gray/Getty Images

WASHINGTON— Friday's nationwide ground stop started when a contractor updated old Federal Aviation Administration telecommunication lines, Transportation Secretary Sean Duffy said Saturday.

Tens of thousands of passengers across the U.S. are still stranded Saturday after the rare ground stop. Bryan Bedford, the FAA administrator who joined Duffy at Saturday's media briefing, said schedule problems should be resolved by Sunday evening.

Nearly 25,000 flights were delayed, and over 9,000 were cancelled on Friday, according to FlightAware, a flight tracking site. The disruption seeped into Saturday morning with more than 4,000 cancellations recorded, which is 18% of flights departing the U.S., according to data from Cirium, an aviation analytics company.

L3Harris, a long time contractor for the FAA, was doing routine maintenance in at least one remote location changing copper wire to fiber optics, Duffy said. "When I tell you that we're using old equipment, we're using old equipment," he said.

He said the FAA is still investigating the exact error that started flooding other routers in the air traffic control system, and if L3Harris was at all responsible.

"It's pretty straightforward work that we were doing yesterday at, again, a very remote location. So what we're working to determine was whether we had incompetence, meaning was it user error, installator error from L3Harris, or did they install a faulty router?"

In a statement on their website, L3Harris said they have been working with the FAA to modernize communication infrastructure, including converting copper wires to a fiber optic system. The contractor said they have completed more than 70% of those conversions. 

"We are supporting the FAA in its investigation to understand the conditions that led to the Nov. 13 ground stop of our nation's air travel," the statement said. "L3Harris takes the nationwide ground stop and its impact on travelers, airlines and air traffic operations seriously."

These updates have been happening in American institutions for decades, Duffy said.

"Virtually every single institution in America has gone from copper to fiber, from analog to digital," Duffy said. "Just maybe the FAA is the last one to be doing this work because the investments haven't been made, but this is not complicated."

Bedford said there was no evidence of anything nefarious happening or any AI-related issues.

Since his time in office, Duffy said he's been asking Congress for money to make more upgrades. In July 2025, Congress approved $12.5 billion to modernize the nation's aging air traffic control system.

On Saturday, Duffy said again that the FAA needed more money for improvements.

"This is the moment, if we don't start to switch out our systems, when, how long are we going to wait, America, and Congress?" Duffy asked.

Thousands of passengers miss flights

Passengers wait at boarding gates at Ronald Reagan Washington National Airport in Washington, D.C. on Friday. Zina Desmazes/AFP via Getty Images hide caption

Zina Desmazes/AFP via Getty Images

For about four hours on Friday, thousands of flights at U.S. airports were grounded in one of the biggest disruptions of the nation's air travel system since the terrorist attacks on September 11, 2001.

The aviation system is back online and slowly returning to normal Saturday morning, but delays and cancellations will continue, Duffy said. Bedford said all passengers will be put on new flights or they'll get a full refund, but that people should reach out to their airlines directly.

Flight boards at airports across the country Saturday morning continued to be riddled with red cancelled marks. At Tampa International Airport in Florida, people in the main terminal area before security curled up in chairs to grab a wink of sleep.

On Friday night, a flight board at Ronald Reagan Washington National Airport in D.C. showed dozens of flights delayed into the early morning hours or cancelled.

Passengers Erin and Jake Britt spent half the day at the airport in D.C. on Friday. Their plane to Fort Lauderdale, Fla. boarded at 3 p.m. By 5:30 p.m., they were getting off the plane — but they were still in D.C.

"Overall, our plane was definitely annoyed, but reasonable," Erin Britt said, as the couple left the airport at 8 p.m. "People being upset and asking like, 'Well, how are you not prepared for this?' And it was like, 'Well, no one was prepared.'"

She said neither the pilot nor flight attendants had any more information than passengers."They seem just as in the dark," she said.

The pair decided to cancel their weekend trip, but the night didn't end there. They spent over nine hours overnight waiting on the JetBlue customer service call line to be reimbursed. "I was setting alarms in 20 minute intervals in case I fell asleep," Erin Britt said.

For people who had events or plans over the weekend – the delay added an extra layer of stress. Joe Romano and Maddie Cabana had a cruise leaving Orlando, Fla. Saturday afternoon.

"It was a big eye roll. I mean, I travel a lot for work already, so I'm constantly dealing with flight delays," Romano said. "When this happened, I was just like, 'Of course, it always happens to me.'"

"Just rather inconvenient and frustrating," Cabana added, as the pair contemplated checking their bags or going home. They even thought about driving to Florida. "Hopefully, everything will be fine. It'll all work out. It always does."

And it did— eventually. After their JetBlue flight was ultimately cancelled, they quickly booked another one on Southwest Airlines and made it early Saturday morning.

Others, like Suze DiPietro decided flying wasn't worth it anymore. Her husband drove about four hours down from Ocean City, New Jersey to pick her up in D.C. Luckily, they had friends in the area where they spent the night.

"My husband, my hero, is driving down from New Jersey to come get me," DiPietro said.

Other alternatives included people switching to Amtrak trains as they struggled to get to their destination. Although, even Amtrak's system had a brief outage Friday night.

This was only the second nationwide ground stop since September 11, 2001. The U.S. last issued a ground stop of this scale in 2023, when all U.S. airports were shut down due to an outage in the NOTAM (Notice to Air Missions) system, which alerts pilots and airports of real-time hazards.

That outage prompted fears of a cyberattack, but the FAA later determined the issue was caused when contract workers inadvertently deleted critical files.

The FAA has recently begun rolling out an AI-enhanced software tool known as the SMART system as part of its ambitious overhaul of the nation's air traffic control system. But Air Space Intelligence, the company that makes the tool, quickly dismissed speculation that its product could be connected to the flight disruptions.

"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 on social media.

Ava Pukatch contributed to reporting.