A corrupt file appears to have been behind the Federal Aviation Administration system outage Wednesday that caused the first national grounding of flights in the US since the 9/11 attacks. The corrupt file was found in the main Notice to Air Missions (NOTAM) system as well as in the backup system, a source tells CNN. What's still unclear is exactly what led to the problem; a source tells the network the FAA is investigating whether a "routine entry" into the database, or any specific person, is responsible for the corrupted file. In a statement late Wednesday, the FAA said, "Our preliminary work has traced the outage to a damaged database file. At this time, there is no evidence of a cyberattack."
The problem was first discovered Tuesday, and sources tell Bloomberg that officials first tried to switch to the backup system before discovering it wasn't working, either. Sources say air traffic control officials decided to reboot the main NOTAM system (a process that can take 90 minutes) early Wednesday in order to cause the fewest flight disruptions. But when the system came back online, it still "wasn't completely pushing out the pertinent information that it needed for safe flight," a source says, leading the FAA to ground all flights around 7:30am Eastern time. (Read more Federal Aviation Administration stories.)