The Federal Aviation Administration issued a nationwide ground stop for all flights due to take off in the United States on Friday, delaying or canceling more than 11,000 US flights according to aviation tracker FlightAware. A ground stop requires aircraft to remain on the ground and bars them from taking off, though planes already in the air are usually allowed to continue. The FAA said the stop was imposed "due to extraordinary circumstances and for reasons of safety."

Transportation Secretary Sean Duffy said in a post on X that the stoppage was caused by "a communication issue impacting all Air Route Traffic Control Centers," and that FAA technicians were looking into the matter. Markwayne Mullin, the Department of Homeland Security director, told reporters that preliminary investigations did not indicate a "nefarious attack," describing it as a telecommunications outage, while adding that officials were not ruling anything out and would continue working to find the root cause.S2

Mullin said the immediate priority was ensuring that planes still in the air could land safely, and that there was no clear information on how long the stoppage might last. ABC News reported that as enroute facilities recovered, flights would be allowed to depart through coordination with the air traffic control system command center, and that the ground stop remained in effect in an update shortly after 6 p.m. ET.S1S2

The disruption drew attention at major hubs. Los Angeles Mayor Karen Bass said she was in close contact with Los Angeles World Airports leadership to receive real-time updates on the impacts, and at Ronald Reagan Washington National Airport, travelers crowded the terminal, with some sitting on the floor as they tried to change their flights.S2

The event is only the third time all departing flights have been grounded in the US, after September 11, 2001 and a January 2023 pause of less than two hours caused by a malfunctioning pilot notification system. The FAA has more than 14,000 air traffic controllers handling more than 44,000 daily flights, and the disruption comes shortly after the first digital air traffic control towers in Alaska and Florida became operational as part of a modernization project meant to reduce delays.S2