US lifts nationwide flight ground stop after 4 hours of air traffic control outage, confirms no cyberattack

The Federal Aviation Administration (FAA) lifted its nationwide flight ground stop after an air traffic control communication outage disrupted operations across the United States, with officials ruling out a cyberattack and saying the public was never in danger.

US Homeland Security Secretary Markwayne Mullin said there was no connection between the incident and Microsoft and confirmed that investigators had found no evidence of a cyberattack.

“There is no cyberattack,” Mullin said, adding that officials were still working through the process of understanding what happened.


US Transportation Secretary Sean Duffy said the disruption began at 3:36 pm when radar and communication systems at air traffic control centres and terminal radar approach control (TRACON) facilities across the country became unstable.

“At [3:36] p.m., we experienced instability in our radar and our communications in our centres and our TRACONs across the country,” Duffy said.

He said the instability caused inconsistencies in radar data and communication with aircraft, prompting officials to issue a ground stop as a safety precaution.

“We had over 3,500 aeroplanes in the air. They all engaged, and last time I looked we had less than 400 in the airspace as they were all coming in to safely land,” Duffy said.

Duffy said the FAA did not shut down all air traffic operations and continued to allow critical flights, including medical evacuations, cargo carrying essential medicines and law enforcement movements.

“We didn't lose all TRACON; we didn't lose all radar, but that instability, because of abundance of caution and making sure we keep the American flyer safe, we did the ground stop,” he said.

US flight disruption: What caused the FAA outage?

The FAA had ordered a nationwide ground stop on Friday after communication problems affected the 22 regional air traffic control centres responsible for directing aircraft travelling between airports across the country.

The restrictions were imposed “due to extraordinary circumstances and for reasons of safety”, the agency had said earlier.

Duffy clarified that the United States had not lost all telecommunications or radar capabilities during the ground stop.

“Didn't lose all telecom, didn't lose all radar during ground stop,” he said.

Mullin said the situation appeared to be improving.

“Right now things seem to be working in right direction,” he said.

He also sought to reassure passengers about the safety of the incident.

“Public was never in danger,” Mullin said.

US flights: Ground stop lifted after nationwide disruption

The nationwide ground stop was the first since January 2023, when a malfunction in a key FAA computer system disrupted air travel. Before that, the last nationwide grounding was imposed following the September 11, 2001, attacks.

At least 600 flights had been diverted during Friday's disruption, according to aviation analytics company Cirium. Several flights were redirected to Chicago O'Hare International Airport, Denver International Airport, Dallas-Fort Worth International Airport and Ronald Reagan Washington National Airport.

Around 11,000 flights carrying more than 1.5 million passengers had been scheduled to depart US airports after 4 pm Eastern on Friday, raising the possibility of widespread delays and cancellations.

United Airlines had said flights already airborne would continue, but new domestic flights would not depart while the FAA ground stop remained in place.

FAA modernisation programme under scrutiny

The disruption has renewed attention on the ageing technology used by US air traffic controllers.

Duffy attributed the disruption to ageing air traffic control infrastructure, saying the outage involved old hardware.

“The President, for the last year, has been asking Congress to fully fund a full build of a brand-new air traffic control system,” he said.

The government has been working to replace outdated systems since Congress approved $12.5 billion for the modernisation programme last year. The overhaul includes replacing copper wires with fibre-optic lines and upgrading radio systems at airports.

However, the work remains incomplete. Duffy has said another $30 billion will be required to finish the programme, while the White House has begun lobbying Congress for additional funding.

A similar communication outage at a regional air traffic control centre in September disrupted hundreds of flights across the Northeast.