The Federal Aviation Administration announced a rare nationwide ground stop on Friday afternoon, in what appeared to be a major outage affecting its air traffic control system.

Sean Duffy, the secretary of transportation, confirmed the outage in a social media post, citing “a communication issue impacting all Air Route Traffic Control Centers.”

“FAA technicians are investigating the issue,” he added. “We will provide immediate updates as we have them.”

The agency posted an advisory stating that “all airports are ground stopped,” citing “extraordinary circumstances and for reasons of safety” as the reasons.

“All departing traffic should remain ground stopped until further notice,” the official advisory read, adding that the landings of inbound international flights would be managed on a case-by-case basis.

Shortly after the advisory was posted, an F.A.A. website that lists air traffic control system notices appeared to have gone down, erasing dozens of notices that previously had been listed.

This is a developing story.