The Federal Aviation Administration halted all departing flights across the United States on Friday, Nov. 13, after a telecommunications outage disrupted communications at air traffic control centers nationwide.

O'Hare International Airport and Midway International Airport were among the first airports affected. The disruption started in Chicago, according to The Air Current aviation news website, which reported the FAA stopped flights bound for O'Hare about 10 minutes after 3 p.m. Eastern time. Midway received the same order three minutes later. Boston, Washington, New York and Minneapolis airports reported problems soon thereafter.

Within an hour, the stop went nationwide.

Transportation Secretary Sean Duffy said on X that the ground stop followed "a communication issue impacting all Air Route Traffic Control Centers." He said FAA technicians were investigating.

The FAA described the problem as "a temporary telecommunications outage" in a post on X shortly after 5 p.m. Eastern. The agency said all flights had been accounted for and that international flights would be handled on a case-by-case basis.

The 22 Air Route Traffic Control Centers mostly manage high-altitude traffic between airports. The communications problems affected those centers, disrupting the system that coordinates aircraft across U.S. airspace.

Homeland Security Secretary Markwayne Mullin told reporters at the White House that the outage had not been linked to a threat or attack, NPR reported. "There is no indication, and we had no reason to believe as of right now that this was a threat to the United States," Mullin said.

What it means for travelers

A ground stop is not the same as an airport closure. Planes already in the air were allowed to continue to their destinations. Departing flights were held at the gate.

United Airlines said its airborne flights would continue but that new domestic flights would not depart while the ground stop remained in place, NBC News reported.

The FAA had not publicly identified the cause of the outage or confirmed when departures would resume as of Friday afternoon. The agency's advisory listed the stop as running through 11 p.m. Eastern for planning purposes, Rolling Out reported, but the FAA's instruction was that departures stay grounded until further notice.

As of 4:48 p.m. Central time Friday, the FAA's National Airspace System Status page showed no active airport events and no command center announcements. Whether that reflected a full or partial lifting of the ground stop was not clear from available information.

Even after the stop is lifted, delays and cancellations could continue as airlines work to reposition planes and crews.

Travelers should check flight status directly with their airline before heading to O'Hare or Midway. The FAA posts live updates at nasstatus.faa.gov.

A rare event

This is only the second nationwide ground stop since the Sept. 11, 2001, attacks, according to Arkansas Radio. The previous one occurred Jan. 11, 2023, when the FAA's Notice to Air Missions system, which sends safety alerts to pilots, failed. That outage led to more than 10,000 flight delays and more than 1,300 cancellations nationwide.

The FAA later determined the 2023 failure was caused when contract workers accidentally deleted critical files, NPR reported.