FAA: Contractors unintentionally deleted files causing outage that grounded thousands of flights

The Federal Aviation Administration says a mistake made by contractors caused an outage that grounded thousands of flights across the U.S.

The official statement was released Thursday night by the FAA.

"A preliminary FAA review of last week’s outage of the Notice to Air Missions (NOTAM) system determined that contract personnel unintentionally deleted files while working to correct synchronization between the live primary database and a backup database," the FAA’s statement read. "The agency has so far found no evidence of a cyber-attack or malicious intent. The FAA continues to investigate the circumstances surrounding the outage."

"The FAA made the necessary repairs to the system and has taken steps to make the NOTAM system more resilient," the statement continued. "The agency is acting quickly to adopt any other lessons learned in our efforts to ensure the continuing robustness of the nation’s air traffic control system."

The system broke down late Tuesday, January 10 and was not fixed until midmorning Wednesday.

The FAA prevented any planes from taking off for a time leading to more than 1,300 flight cancellations and 9,000 delays by early evening across the East Coast.

The breakdown showed how much American air travel depends on the computer system that generates alerts called NOTAMs — or Notice to Air Missions.

Before a plane takes off, pilots and airline dispatchers must review the notices, which include details about bad weather, runway closures or other temporary factors that could affect the flight. The system was once telephone-based but moved online years ago.

The Associated Press contributed to this article