Image: Getty/The Washington Post

A corrupt database file is to blame for the computer system outage at the Federal Aviation Administration (FAA) that temporarily grounded all domestic flights across the US -- but it's still uncertain what caused damage to the database file.

The incident caused mass disruption and delays for airlines, airports and passengers.

It seems it was related to an issue with the Notice to Air Missions (NOTAM) system, which provides pilots with real-time information about changes and potential hazards on flight routes. The lack of system availability meant that all domestic flights were temporarily grounded for two hours while the system was restored.  

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"Safety is always our first priority, and ensuring flight safety was the reason for this morning's ground stop while the affected systems were restored and checked. As normal flight operations have resumed, FAA continues to assess the causes of the outage," said transportation secretary Pete Buttigieg at the time.

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Now the FAA -- the US government agency that oversees many aspects of America's aviation, including air traffic management -- has revealed it was a database issue that caused the disruption. 

"The FAA is continuing a thorough review to determine the root cause of the Notice to Air Missions (NOTAM) system outage. Our preliminary work has traced the outage to a damaged database file," the agency said in a statement. 

It's currently unclear what happened to corrupt the database file, but according to the FAA, "at this time, there is no evidence of a cyber attack" and the investigation continues.  

"The FAA is working diligently to further pinpoint the causes of this issue and take all needed steps to prevent this kind of disruption from happening again," the agency added. 

The disruption caused problems for air travellers, who suffered from delays and cancellations, and President Biden was even briefed on the NOTAM system outage.

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