When air traffic control officials realized they had a computer issue late Tuesday, they came up with a plan: Reboot the system when it would least disrupt air travel Wednesday morning.
Ultimately, that plan and the outage led to massive flight delays and an unprecedented order to stop all aircraft departures nationwide, a source familiar with the Federal Aviation Administration operation told CNN.
FAA officials told reporters early Wednesday that the issues developed in the 3 p.m. ET hour on Tuesday.
Officials ultimately found a corrupt file in the main Notice to Air Missions, or NOTAM, the source said. A corrupt file was also found in the backup system. The NOTAM is a critical and enormous safety computer system that advises pilots of issues along their route and at their destination. It has a backup, which officials switched to when problems with the main system emerged, according to the source.
In the overnight hours of Tuesday into Wednesday, FAA officials decided to shut down and reboot the main NOTAM system – a significant decision, because the reboot can take about 90 minutes, according to the source.
They decided to perform the reboot early Wednesday before air traffic began flying on the East Coast in order to minimize disruption to flights.
“They thought they’d be ahead of the rush,” the source said.
During this process, the FAA told reporters that the system was “beginning to come back online,” but said it would take time to resolve.
The system, according to the source, “did come back up, but it wasn’t completely pushing out the pertinent information that it needed for safe flight, and it appeared it was taking longer to do that.”
That’s when the FAA issued a nationwide ground stop at around 7:30 a.m. ET, halting all domestic departures. Aircraft in line for takeoff were held before entering runways. Flights already in the air were advised verbally of the safety notices by air traffic controllers, who keep a static electronic or paper record at their desks of the active notices.
Transportation Secretary Pete Buttigieg ordered an after-action review and said that there was “no direct evidence or indication” that the issue was a cyberattack.
The source said the NOTAMS system is an example of aging infrastructure due for an overhaul.
“Because of budgetary concerns and flexibility of budget, this tech refresh has been pushed off,” the source said. “I assume now they’re going to actually find money to do it.”
“The FAA’s infrastructure is a lot more than just brick and mortar.”
The FAA did not immediately respond to a CNN request for comment on this account.