Planes sat parked at gates from coast to coast Friday night after federal aviation officials ordered every airport in the country to stop sending flights into the sky. The order came just before 3 p.m. Central time, when the facilities that steer airliners between cities began losing their radio channels and radar feeds one after another.

Transportation Secretary Sean Duffy blamed a communications breakdown that touched all of the regional en route centers. Those 22 sites handle jets once they climb past 18,000 feet, so when their links fail, controllers lose the ability to talk to crews and track traffic across huge stretches of the map. Duffy said technicians were working to find what went wrong.

Homeland Security Secretary Markwayne Mullin told reporters at the White House that officials had found nothing so far pointing to a hack or a terror plot. He described it as a phone and data outage, told the public there was no reason to be frightened for loved ones in the air, but said investigators were not ruling anything out yet. He added that it was too soon to say when normal service would come back.

Early accounts traced the first trouble to the center that covers the Chicago region, with Boston, Washington, New York and Minneapolis reporting problems minutes later. Officials first halted traffic bound for the eastern half of the country, then widened the order to every airport as more facilities went quiet. Flights already airborne were allowed to finish their trips, though many were sent to smaller cities because big hubs ran out of open gates.

A national halt of this kind is extremely rare. The only other time every departure in the country was frozen for this long came after the attacks of Sept. 11, 2001. A shorter nationwide pause happened in January 2023 when a pilot warning system crashed.

By early evening the stop was set to run until at least 10 p.m. Central. A trickle of planes was being cleared case by case, including flights within Hawaii and Alaska, Pacific crossings out of San Francisco and some flights to Europe from Boston and New York. Travelers at San Francisco broke into cheers when the first jets finally rolled down the runway.

The cancellations piled up fast. Flight tracking data showed thousands of trips scrapped on Friday and hundreds more already wiped from Saturday's schedule. United said it would cancel most of its remaining flights for the night. JetBlue said it was dropping everything left on Friday except some Europe departures and warned that the mess would spill into the weekend. American said most departures were still paused even as a few got the green light.

Several carriers waived change fees so customers can rebook without paying more. Delta said its waiver covers both Friday and Saturday.

The outage arrived only days after the agency switched on a new AI scheduling tool at all 22 en route centers. Officials said they were looking at any possible link, while the company that built the tool said flatly that its software did not cause the shutdown. Anyone flying this weekend should check with the airline before heading to the airport.