FAA ground stop live updates: Air travel expected to recover by end of Sunday, FAA chief says

More than 1,600 flights have been cancelled Sunday as airlines work to recover their operations following Friday's ground stop.

Some 1,627 flights have been cancelled as of late Sunday morning, per FlightAware. According to Cirium, an aviation analytics company, roughly 5% of flights in the U.S. are cancelled Sunday.

American and JetBlue are being hit harder than the others. American has cancelled 472 flights Sunday -- about 13% of their operation -- while JetBlue has cancelled 251 flights, or roughly 27% of their operation.

More than 17,500 flights were cancelled Friday and Saturday. Only 30 Monday flights had been cancelled as of late Sunday morning.

Transportation Secretary Sean Duffy said on ABC's "This Week" Sunday that “we’re going to see things come back to normal today, but probably fully normal tomorrow.”

-ABC News' Clara McMichael

Transportation Secretary Sean Duffy said Sunday that air traffic control routers' ability to broadcast data has been turned off as officials continue to investigate the router communication issue that prompted a nationwide ground stop Friday.

"We have that router in the L3 Harris lab down in Florida," Duffy told co-anchor Martha Raddatz on ABC's "This Week" Sunday, referring to the specific router in Arkansas that officials believe caused instability in the air traffic communication system Friday afternoon. L3 Harris is a government contractor that provides technology and IT support for the Federal Aviation Administration (FAA).

"Our FAA team is on site as well. We've been partnering with the FBI and other law enforcement. We're going to take a look at what happened there," he continued. "But what we've now done, we have 69 of these routers in the national airspace. We've stopped their ability to broadcast, and it was this router was broadcasting data from this this radio facility into the whole network. Once we shut the shut the ability to broadcast down on the routers, the issue is resolved. So we're going to take a hard look at it."

Duffy explained that work was being done to replace outdated copper wire with fiber cables in El Dorado, Arkansas. When the router in that area was turned on, "we saw that in Amarillo, Texas, a system we had replaced about three weeks earlier, that started to flood our system as well."

"So we're looking at those two issues and trying to find the root cause of what happened," Duffy said.

-ABC News' Quinn Scanlan

In his first public comments about the nationwide FAA ground stop that took place on Friday, President Donald Trump blamed the Biden administration for “making an old and broken system worse than when they began.”

“The Biden Administration was an FAA disaster. Everything they touched turned bad. Big money spent unwisely, making an old and broken system worse than when they began,” Trump wrote on his social media platform Sunday morning.

Trump also repeated the administration’s desire for Congress to approve additional funding.

“We have the knowledge and plan for the Flight Control Systems, we need Congress to give the money, FAST! Our FAA is doing a great job, and is ready to go,” Trump said.

In a subsequent post, the president again made the case for Congress to provide funding to help modernize the U.S. air traffic control system.

“If Congress approves the desperately needed money for Air Traffic Control, we can get it built quickly and efficiently. It will be the BEST SYSTEM anywhere in the World. Much of our current air control system is 50 years old - RIDICULOUS!” Trump wrote.

On Friday, Transportation Secretary Sean Duffy requested $50 billion from Congress to update these systems.

“We have already started the work, but it should be done all at once, not in drips and drabs. Congress must approve. The Biden Administration set it back years!” the president added.

More than 14,000 flights were cancelled Friday and Saturday, with an additional 900 flights cancelled as of early Sunday.

-ABC News' Emily Chang

Some travelers on Sunday could be in for another rough day -- with over 900 flights already canceled.

According to FlightAware, 910 flights have been canceled Sunday, and the number is rising.

American Airlines is extending its travel alert and waiving change fees for travel scheduled through Wednesday, Nov. 18.

"American’s recovery from yesterday’s FAA nationwide ground stop continues to move forward," the company said in a statement. "All planned cancellations for tonight and tomorrow have now been completed, though some individual flights may still be canceled as we continue working to fully restore the operation. Our focus tonight is on setting up the operation for a strong start tomorrow, with our crews and aircraft positioned to get customers on their way."

Delta Airlines is encouraging travelers with flexible plans to move their flights to Monday or further out.

Overall, more than 6,400 flights were canceled on Saturday, according to FlightAware, on top of more than 9,000 flights canceled on Friday.

-ABC News' Clara McMichael