The US Federal Aviation Administration says the flight personnel alert system does not process updates after an outage

The Civil Aviation Organization’s website showed on Wednesday that the US Federal Aviation Administration (FAA) system that alerts pilots and other flight personnel about risks or any changes to airport facility services and related procedures did not process the updated information.

In an advisory, the FAA said its NOTAM (Notice to Air Missions) system “failed.” There is no immediate estimate of when it will return, the site showed, although NOTAMs issued before the outage are still viewable.

Flight-tracking website FlightAware showed that more than 400 flights were delayed in, in or out of the US as of Wednesday 5.31am ET. It was not immediately clear if the power outage was a factor.

“Technicians are currently working to restore the system,” the website showed. The FAA could not immediately be reached for comment.

A NOTAM is a notice that contains basic information for personnel involved in flight operations, but is not sufficiently known in advance to be disseminated by other means.

The information can be up to 200 pages long for long-haul international flights and may include items such as runway closures, general warnings of bird hazards, or low-altitude construction obstacles.