F.A.A.’s Main Warning System for Pilots Is Down, U.S. Official Says

The Federal Aviation Administration was using a backup system to send real-time safety alerts to pilots late Saturday because its primary one was “experiencing a temporary outage,” the Transportation Department said.

“The primary NOTAM system is experiencing a temporary outage, but there is currently no impact to the National Airspace System because a backup system is in place,” Transportation Secretary Sean Duffy said on social media.

Mr. Duffy was referring to “Notice to Air Missions,” the alerts that the F.A.A. uses to share information about hazards in the air or on the ground, such as closed runways, airspace restrictions and navigational signal disruptions.

He said the F.A.A. was working to fully restore the system and that the agency would provide updates on its status every 30 minutes. But he warned of possible “residual” flight delays on Sunday morning.