The Federal Aviation Administration system failure on Wednesday was caused by a damaged file, which was initially reported by CNN. Officials are still working to determine exactly what caused it.
The FAA stated in a statement issued late on Wednesday that it was still looking into the outage and will "take all necessary precautions to avoid this kind of disruption from happening again."
"Our first investigation has linked the outage to a corrupt database file. There is currently no proof of a cyberattack, "said the FAA.
According to a government official with knowledge of the inquiry into the NOTAM system breakdown, the FAA is still attempting to ascertain whether a single individual or "routine entry" into the database is to blame for the corrupted file.
On Wednesday, a different person familiar with the Federal Aviation Administration's operations gave CNN an exclusive account of how the outage unfolded.
According to the source, air traffic control authorities devised a plan to reboot the system early on Wednesday morning after realising they had a computer problem late on Tuesday.
However, as a result of the outage and the plan, there were a lot of flight delays and a nationwide order was issued to halt all takeoffs of aircraft.
The national NOTAM (Notice to Air Missions) database was housed in the computer system that malfunctioned. These notifications inform pilots of problems on the way and at the destination. It has a backup, which administrators switched to when issues with the primary system were discovered, the source claims.
Early on Wednesday, FAA officials told reporters that the problems began to arise around 3 p.m. ET on Tuesday.
The source told CNN that officials eventually discovered a faulty file in the primary NOTAM system. The backup system also contained a corrupt file.
FAA authorities opted to shut down and restart the primary NOTAM system overnight on Tuesday and into Wednesday. This was a big move because, according to the source, a reboot can take up to 90 minutes.
To minimise the impact on flights, they chose to do the reboot early on Wednesday, before aviation traffic started to travel along the East Coast.
The insider claimed that "they believed they'd be ahead of the rush."
The FAA told reporters during this early morning procedure that the system was "starting to come back online," but added that it would take time to fix.
The system "did come back up, but it wasn't totally pushing out the important information that it needed for safe flying, and it appeared that it was taking longer to accomplish that," the insider said.
Around 7:30 a.m. ET, the FAA imposed a nationwide ground stop, stopping all domestic departures.
Before entering runways, aircraft waiting to take off were held. Air traffic controllers, who keep a static computer or paper record of the active notifications at their desks, verbally informed flights already in the air of the safety notices.
There was "no direct evidence or suggestion," according to Transportation Secretary Pete Buttigieg, that the problem was the result of a cyberattack. He also mandated an after-action study.
The NOTAM system, according to the source, is an example of outdated infrastructure that has to be upgraded.
