An error by "contract personnel" led to the grounding of flights across the US last week for the first time since the 9/11 attacks, according to the Federal Aviation Administration. The unnamed personnel accidentally deleted files on the Notice to Air Missions (NOTAM) database, which notifies pilots of potential hazards, "while working to correct synchronization between the live primary database and a backup database," the FAA said Thursday, per Axios. The agency had previously referred to a damaged database file.
The NOTAM system, which pilots must check before taking off, went offline, temporarily grounding all departures in the US on the morning of Jan. 11. Some 11,000 flights were delayed and another 1,300 were canceled, per the BBC. Axios reports airlines lost billions of dollars. The FAA said it is continuing to investigate but "has so far found no evidence of a cyber-attack or malicious intent." It also said it "has taken steps to make the NOTAM system more resilient." FAA acting Administrator Billy Nolen will address lawmakers, who demanded answers following the disturbance, on Friday. (Read more FAA stories.)