FAA Ground Stop Halted U.S. Flights for More Than Four Hours

The Federal Aviation Administration halted U.S. departures for more than four hours Friday after communications failed at several air route control centers, disrupting thousands of flights.

The ground stop began at about 4 p.m. ET and ended at 8:15 p.m. ET. More than 5,300 flights were canceled that day.

Transportation Secretary Sean Duffy blamed outdated switches and routers overwhelmed by data, which he said began sending inconsistent information. He said officials shut down the system in response.

Homeland Security Secretary Markwayne Mullin said officials did not believe the disruption was a cyberattack, but would not rule one out while the investigation continued.

The FAA had expanded its SMART AI air-traffic assistance system to all 22 U.S. en route centers on Nov. 10. No official has linked SMART to the communications failure. The system's contractor, Air Space Intelligence, said its software did not cause the flight halt.