FAA ground stop live updates: Flight cancellations continue into Monday

The CEO of United Airlines called Friday's nationwide ground stop a "call to action" in a statement posted on the airline's website Sunday.

Scott Kirby said that although the FAA "took decisive action to keep our airspace safe and secure" and air traffic controllers and their leadership "worked around the clock" to mitigate the effects of the ground stop, "our Air Traffic Control system needs more investment in modern technology to ensure better redundancy and reliability now."

"This moment must be a call to action," Kirby said. "It is critical for safety, our passengers, and our economy that we fix our nation’s Air Traffic Control system now," adding that the FAA needs "100% staffing and to have the funds to modernize the technology. And they need and deserve 100% support from all of us."

Kirby also said he'd "spoken directly with the Secretary of Transportation and the FAA Administrator" about the ground stop and its effect on United and its customers, as well as "leaders on both sides of the aisle in the last 24 hours and can confirm that they’re committed to modernizing the U.S. ATC system while holding the FAA accountable at the same time."

"I am proud of each and every one of our United Airlines team members" who worked to mitigate the ground stop disruptions, Kirby said, also thanking customers "for their patience as our teams worked to get them safely to their destinations and keep them informed along the way."

Nearly 2,300 flights in the U.S. have been cancelled Sunday in the aftermath of Friday's nationwide ground stop.

FlightAware reported 2,291 total flight cancellations as of 3 p.m. ET Sunday. That's up from just over 1,600 cancelled flights reported late Sunday morning, as airlines work to recover their operations.

Additionally, some 18,689 flights were delayed, per FlightAware. American Airlines had the most flights reported cancelled, with 611, followed by JetBlue with 253 and SkyWest with 207.

Total cancellations reported for Monday stood at 144 as of Sunday afternoon, according to FlightAware, with 641 delayed.

A spokesperson for Hewlett Packard Enterprise, which owns Juniper, the company that manufactured the routers believed to be central to the ground stop, said in a statement to ABC News that the devices were working properly Friday, when the ground stop occurred.

"Based on what we know today, the device functioned as it was configured to by the installer. It did not fail or act improperly," the statement said.

The routers are now being examined at an L3Harris lab in Florida. L3 Harris is a government contractor that provides technology and IT support for the Federal Aviation Administration (FAA) and that worked with Hewlett Packard Enterprise and Juniper to install the routers.

"We have that router in the L3 Harris lab down in Florida," Transportation Secretary Sean 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.

"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. L3Harris takes the nationwide ground stop and its impact on travelers, airlines and air traffic operations seriously," L3Harris said in a statement Saturday.

-ABC News Ayesha Ali

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