WASHINGTON (AP) — The Federal Aviation Administration (FAA) ordered a rare nationwide ground stop for all departing flights across the U.S., citing unspecified safety concerns.
The emergency directive took effect at 3:54 PM Eastern Time on Friday, with all departing aircraft instructed to remain on the ground until further notice.
According to the advisory, international flights arriving in the U.S. were handled on a case-by-case basis. The ground stop was lifted around four and a half hours later, although flight disruptions continued.
Around 1,900 flights were canceled and 10,500 delayed as of 6:00 PM Eastern Time on Friday, ABC13 reported, citing flight-tracking service FlightAware.
U.S. Transportation Secretary Sean Duffy said the nationwide ground stop was prompted by a “communication issue impacting all Air Route Traffic Control Centers.”
“FAA technicians are investigating the issue. We will provide immediate updates as we have them,” he wrote on X.
Preliminary reports suggest the disruption was not caused by a cyberattack, CNN reported, citing two law enforcement officials.
Homeland Security Secretary Markwayne Mullin said the grounding was caused by a “telecommunications outage,” which the authorities do not believe was the result of foul play.
Duffy later blamed the shutdown on the “incredibly old” air traffic control system.
“Our switches, our routers, actually got overloaded with data... and started to give us inconsistency in the data from those routers,” he said at a news conference.
The National Weather Service also reported nationwide internet and communications problems, warning that some weather information on its websites could be unavailable or outdated. The agency said technicians were working to restore services.
The last nationwide ground stop was ordered in January 2023 following a failure of the system that provides safety notices to pilots. The previous shutdown occurred in the immediate aftermath of the September 11, 2001 terrorist attacks.
The outage came just days after the FAA announced the nationwide rollout of SMART, a new AI-powered system designed to optimize flight routes and reduce delays. It was deployed across all 22 regional air traffic control centers, although the authorities have not established whether it played any role in Friday’s disruption.
Similar technical failures have disrupted air travel worldwide this year. In September, a communications outage halted flights at major airports in the northeastern U.S., while a software malfunction caused widespread flight cancellations across Britain. Greece temporarily closed its airspace in January, and Italy halved its air traffic capacity following a technical failure in October.