US aviation regulator probing system outage after huge disruption

WASHINGTON - Aviation authorities were racing to figure out what caused the outage of a crucial alert system that forced the temporary halt on all US domestic takeoffs, triggering thousands of delays and cancellations.

The US Federal Aviation Administration (FAA) said normal operations were being restored but the early morning halt created knock-on effects that snarled travel throughout the day.

The grounding order was issued after the FAA identified an issue with the Notice to Air Missions system (NOTAM), which provides information to pilots about hazards, changes to airport facilities and information that can affect flights.

"Our preliminary work has traced the outage to a damaged database file," the FAA said in a tweet Wednesday evening, adding that "at this time, there is no evidence of a cyberattack."

READ: Flights gradually resuming in US after nationwide stoppage

The temporary outage spelt yet another hellish day for US travellers -- less than a month after a bad winter storm roiled the system.

Wednesday's nationwide order was believed to be the first time since the attacks of 9/11 that such a broad command had been issued, according to aviation experts cited in US media.

The FAA did not respond to queries seeking confirmation.

Flying experts say the system in question contains a range of highly relevant details, such as a closed runway, to less significant matters, like the presence of a crane somewhere in or near the airport.