Seattle-area travelers faced disrupted departures at Seattle-Tacoma International Airport on Friday, Nov. 13, after the Federal Aviation Administration ordered a nationwide ground stop because of a telecommunications outage affecting air traffic control centers.

Some international departures were later allowed. In an update posted at 3:58 p.m. Pacific, MyNorthwest reported that Port of Seattle spokesperson Perry Cooper said Asia-bound flights had been cleared to leave SEA. That did not establish a full resumption of domestic departures.

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 noon Pacific 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 2 p.m. Pacific. 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.

When the nationwide order was issued, the cause of the outage and a timetable for resuming departures were not publicly confirmed. The advisory listed the stop as running through 8 p.m. Pacific for planning purposes, Rolling Out reported. That planning time was not a guarantee that normal operations would resume then.

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 SEA or another Puget Sound airport. The FAA posts live updates at nasstatus.faa.gov.

A rare event

Nationwide ground stops are rare. 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.