Main FAA Warning System, NOTAM, Is Down

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.

As of 2 a.m. Eastern time Sunday, there had been no further updates about the outage on Mr. Duffy’s official social media accounts or on those of the F.A.A. or the Transportation Department.

The F.A.A.’s website had a notice explaining that the agency’s technicians were working to restore “service outages” to the NOTAM system. It was not immediately clear if those outages were in the main NOTAM system or in the backup system, or both, or whether any progress had been made since Mr. Duffy’s announcement late Saturday. The agency did not immediately respond to a request for comment.

The national airspace system of the United States covers an area of more than 29 million square miles, and the F.A.A. provides air traffic service to more than 45,000 flights a day across that area, according to the agency.

The F.A.A. has been in the process of modernizing the NOTAM system, which has gone down before. After a January 2023 outage, departures across the country were halted for about 90 minutes.

This is a developing story.