What Is the NOTAM? Flights Grounded Across U.S. After Major System Outage

All flights have been grounded and paused across the U.S. early this morning until 9 a.m. EST after the Federal Aviation Administration's NOTAM (notice to air missions) system failed, causing travel chaos across the country.

The FAA asked in a statement for time "to allow the agency to validate the integrity of flight and safety information." The FAA has said it systems was coming back online but that the NOTAM systems was still being restored.

The NOTAM mechanism is used by the FAA to deliver essential information that is not known far enough in advance to be publicized by any other means, according to the civil aviation body's website.

This could include plane accidents or other hazards, as well as a change in condition of an aeronautical facility, service or procedure.

The system gives pilots and other flight personnel real-time updates on any abnormalities in the National Airspace System, the FAA said.

NOTAMs can also be issued by national authorities for reasons including closed runways, military exercises resulting in airspace restrictions or the temporary erection of obstacles near airfields, such as cranes.

On Wednesday morning, the Air Traffic Control System Command Center said the NOTAMs outage was affecting U.S.-based airlines, admitting that passengers may face long delays.

"Since the failing of the systems, no new NOTAMs or amendments have been processed. Technicians are currently working to restore the system and there is no estimate for restoration of service at this time," the center said on its website.

More than 500 flights have been grounded across the U.S. as the FAA scrambles to fix the system.

It is unclear what has caused the system malfunction.

Flights have reportedly been delayed at airports including Honolulu, Philadelphia and Tampa, as well as Ronald Reagan Washington airport in Arlington, Virginia.

"The FAA is working to restore its Notice to Air Missions System," the aviation body tweeted on Wednesday morning. "We are performing final validation checks and reloading the system now. Operations across the National Airspace System are affected. We will provide frequent updates as we make progress."

Alex Macheras, an aviation analyst, told Newsweek: "NOTAMS are essential for the safe continuation of global air travel, and these essential notices and directives ultimately keep the world's aviation sector, specifically flight crew and all personnel concerned with flight operations, informed and up to speed with latest air travel related directives, operational updates, security, weather and warnings."

U.S. President Joe Biden has called for a full investigation of the FAA system outage.

His spokesperson, Karine Jean-Pierre, said there was "no evidence of a cyberattack at this point" but that the president advised the Department of Transport to conduct a full probe into the causes and the FAA would provide regular updates.