US officials are still investigating what triggered a nationwide flight halt on Friday, 14 November 2026, after older air traffic control equipment became overloaded, with the Department of Homeland Security confirming it had found no evidence of a cyberattack — but stressing it had not ruled one out. The ground stop, which affected airspace across the United States, has left airlines scrambling to manage a backlog of delayed and cancelled flights.

What Triggered the Disruption

Transportation Secretary Sean Duffy said the problems began at approximately 3:36 pm Eastern Time, when air traffic control centres and terminal radar facilities started receiving inconsistent radar and communications data. At that moment, more than 3,500 aircraft were airborne over US airspace. Duffy attributed the disruption to overloaded legacy equipment but acknowledged that officials were still working to establish precisely what went wrong.

Duffy clarified that radar and communications had not been completely lost. Pilots and controllers followed established emergency procedures to bring aircraft down safely. Essential medical and law enforcement flights were permitted to continue throughout the disruption.

Cyberattack Concerns and What Investigators Found

Homeland Security Secretary Markwayne Mullin, speaking at a White House briefing alongside Duffy, said investigators had found no evidence of a cyberattack and no signs that anyone had accessed the system. However, he stressed that the inquiry was continuing and that officials were not ruling anything out. Mullin also confirmed the disruption was not connected to a separate Microsoft outage that occurred around the same time.

The Legacy Equipment Problem

Both Duffy and Mullin pointed to the age of the US air traffic control network as a central factor. Mullin suggested that newer equipment and technology had overwhelmed the older analogue system. When a reporter asked whether FAA patching had caused the outage, Duffy said it had not, clarifying that the older analogue infrastructure had been overloaded with data, while upgraded digital equipment had not experienced the same problem.

The Federal Aviation Administration lifted the nationwide ground stop on Friday evening after officials took steps to reduce the load on the network. The FAA's air traffic control network spans airport towers, terminal radar facilities, and en route centres — all of which rely on communications and surveillance systems to guide aircraft through US airspace.

Impact on Passengers and Airlines

Duffy warned that restoring normal flight schedules would take time, as airlines assessed the availability of pilots and cabin crews following the disruption. He said getting passengers to their destinations would depend in part on crew availability — a persistent post-disruption bottleneck in the US aviation sector. This comes amid longstanding concerns about underinvestment in the FAA's ageing infrastructure, a subject of repeated congressional debate but limited action.

Investigation Ongoing

As of the White House briefing, no final explanation had been established for what triggered the overload. Duffy said his team was still examining the details and did not want to provide incorrect information before the investigation was complete. Further updates from the FAA and the Department of Homeland Security are expected in the coming days.