At 3:36 p.m. on Friday, US air traffic control radar and communications systems began providing inconsistent data. Eighteen minutes later, an exceptional decision was made: to halt departures at airports across the United States.
About 3,500 aircraft were airborne at the time, while those on the ground faced a wait of more than four hours. According to ABC, this was only the second nationwide ground stop since the September 11 attacks, following the outage in January 2023.
The halt was caused not by a winter storm, but by a failure in the infrastructure that enables controllers to manage air traffic. Transportation Secretary Sean Duffy explained that aging routers and switches had been overwhelmed by data and began transmitting inconsistent information. He said communications and radar data were not lost entirely, and aircraft already airborne were landed safely using existing procedures.
At airports, the outage developed into a full-blown crisis. Reuters reported tens of thousands of stranded passengers, more than 6,600 canceled flights and 8,600 delays. The ground stop was lifted at 8:15 p.m. Eastern Time, but Duffy made clear that departures would resume gradually.
Reopening the runways was only the first step toward restoring normal operations. Airlines had to contend with aircraft and crews stranded in the wrong locations, as well as mandatory rest requirements for pilots and flight attendants. According to Business Insider, the disruption could last for days: Even an aircraft ready for departure cannot take off without an available crew.
The impact extended beyond the United States. According to AP, departures from Europe to the United States were also temporarily suspended at the request of the Federal Aviation Administration. By Saturday, more than 2,500 additional flight cancellations had been reported in the United States.
Administration officials said there was no indication of a cyberattack at this stage, but the investigation had not yet been completed. Duffy directed his criticism at aging infrastructure and Congress, calling for $50 billion to modernize the air traffic control system. "Give us the money to fix it," he said.