The Federal Aviation Administration lifted a nationwide ground stop at 8:15 p.m. ET Friday, nearly five hours after telecommunications failures at air traffic facilities halted departures with more than 3,500 aircraft airborne.

Overloaded Legacy Switches Blamed for FAA Outage

Transportation Secretary Sean Duffy said radar and communications became unstable at 3:36 p.m. ET at terminal radar approach control facilities (TRACONs) and en route centers.

"Our switches, our routers actually got overloaded with data," Duffy said at a news conference, citing the FAA's analog telecom network. He said upgraded IP-based switches did not fail. "It's the old hardware that went down."

No Cyberattack Evidence; Duffy Seeks $50 Billion

Homeland Security Secretary Markwayne Mullin said officials have seen "zero evidence" of a cyberattack and no link to Thursday's Microsoft Corp. (MSFT) email outage, though he did not fully rule it out.

Duffy also asked Congress for $50 billion on top of the $12.5 billion approved in last year's budget law. "This is an emergency," he said. He warned, "You will have more of these," without full funding.

When asked whether the disruption could cascade into Thanksgiving travel, Duffy said he expects the system to be "back up and operational" as Thanksgiving travel peaks, though he acknowledged it will take time to clear the backlog.

The FAA said it tested its systems before clearing flights to resume. It urged passengers to contact their airlines for updates.

Nationwide ground stops are rare. The last one came in January 2023, when a contractor unintentionally deleted files tied to a pilot safety system, and before that only after the Sept. 11, 2001, attacks.

The story is developing. Please check back later for updates.