FAA ground stop live updates: Duffy blames 'overloaded' routers; thousands of flights canceled

On how long to expect delays and cancellations due to the ground stop, Transportation Secretary Sean Duffy told reporters, "I believe that it's going to take us some time to get back to capacity."

He said, it's going to take us some time to unwind what's happened this afternoon," adding that "hopefully tomorrow we are going to start to see far better movement."

Duffy said he believes things will be "back up and operational" heading into Thanksgiving travel.

Pressed on whether the administration can say with 100% certainty this wasn't a cyberattack, Homeland Security Secretary Markwayne Mullin responded, "There's nothing completely certain right now," then said, "It doesn't appear that way."

"There is nothing that indicates it yet," he continued, saying there hasn't been any evidence of an entity claiming to be behind one.

"It appears that this was mechanically driven. However, we're still looking, so we're not going to rule that out," Mullin said.

Transportation Secretary Sean Duffy said that "inconsistency" in data from routers in the air traffic control system led to the FAA issuing a nationwide ground stop Friday.

At 3:36 p.m, "we experienced instability for our radar and our communications in our centers and our TRACONs across the country," he said, referring to Terminal Radar Approach Control facilities.

Duffy described an "incredibly old air traffic control system" that uses analog telecom.

"Our switches, our routers, actually got overloaded with data ... and started to give us inconsistency in the data from those routers. And because of that, we shut the system down," he said.

Homeland Security Secretary Markwayne Mullin reiterated that there was "no cyberattack" at the top of a press briefing Friday on the ground stop.

"I just want to reiterate this: The public was never at danger through this process. There was never any lives at risk. There was no flights at risk," he said.