A nationwide FAA ground stop on Friday, November 13, halted U.S. air traffic after a communication issue affected all Air Route Control Centers, with technicians investigating amid safety concerns.

The disruption lasted a little over four hours, grounding more than 3,500 flights; the FAA lifted the stop by 5:15 p.m. PT, though flights resumed shortly after 8 p.m. according to the account.

After flights resumed, Sean Duffy and Markwayne Mullin said the outage was not caused by artificial intelligence or a cyberattack, but by aging infrastructure that needed updating.

Duffy pointed to old switches, routers and copper lines, while saying newer equipment installed by the Trump administration had not failed.

Duffy said modernization required funding from Congress and acknowledged that the upgrade work may have contributed to instability, though he argued leaving the system untouched posed greater risks.

He also said the FAA had received $15 billion over 25 years to fix air traffic control, but barely anything had been done.

The outage prompted WME executive chairman Ari Emanuel to criticize Pete Buttigieg on X, accusing him of making “zero progress” modernizing the FAA during his four years as transportation secretary.

Emanuel acknowledged that responsibility extended beyond Buttigieg, but said he had left a failing system in operation.

Emanuel’s post drew more than 3,000 responses, with many commenters questioning why he blamed Buttigieg before the cause of the failure was established and challenging his focus on the former secretary rather than Duffy.

Buttigieg was stranded at Denver airport and, after watching Duffy and Markwayne Mullin’s press conference, told The New York Times, “I have questions.”

He praised the public servants responding to the outage and questioned why the aviation system’s redundancies had not prevented a disruption of this scale.

Buttigieg said that during outages in his tenure he focused on resolving the problem rather than blaming the previous administration, and urged officials to keep the response nonpolitical.