The FAA said the stop was "due to extraordinary circumstances."


The Federal Aviation Administration ordered a nationwide ground stop Friday for all airports due to a communication issue affecting air traffic control.
The agency's alert said the stop was "due to extraordinary circumstances and for reasons of safety."
Transportation Secretary Sean Duffy said in an X statement a short while later that the stop was "due a communication issue impacting all Air Route Traffic Control Centers."
"FAA technicians are investigating the issue," he said in an X post.
This is the second time since Sept. 11, 2001, that the FAA has ordered a nationwide ground stop. The last time was in 2023, when the FAA NOTAM system went down and pilots could not get their pre-departure paperwork.
Air Route Traffic Control Centers are responsible for all flights above 18,000 feet. There are 22 of those centers in the U.S.
Pilots who are in the air have flight plans and are prepared to continue with their flight path in case of such an emergency, according to ABC News contributor John Nance.
"All pilots in that environment know what to do," Nance told ABC News on Friday.
Earlier in the afternoon, the FAA issued a ground stop at both Chicago's O'Hare and Midway airports due to equipment outage.
This is a developing story. Please check back for updates.