The overnight outage of a Federal Aviation Administration alert system snarled air traffic Wednesday morning, leading to the first nationwide grounding since the September 11, 2001, terrorist attacks.
Air traffic operations were “resuming gradually,” the aviation regulator said in its most recent update. All flights already in the sky are safe to land, the regulator emphasized in a tweet.
Airlines are now coping with delays and cancellations, while passengers are coping with a new round of headaches after holiday travel. By late Wednesday morning, there were more than 6,700 delays for flights within the U.S. or coming into or going out of the country, according to data from FlightAware. There were just over 1,000 cancellations, the data showed.
At the center of it all is the “Notice to Air Missions system,” which alerts pilots to issues like closed runaways, equipment outages and other possible hazards along a flight route or a destination.
An alert from the system has “information essential to personnel concerned with flight operations but not known far enough in advance to be publicized by other means,” the FAA noted.
*”A person about to drive their car to a destination would want to know the weather outside, the weather where they are going and the best way to get there,” Michael McCormick, an assistant professor at Embry-Riddle Aeronautical University, told reporters Wednesday
“In aviation, it’s done all through NOTAMS,” McCormick said, explaining that airlines and airports can generate the notices that give heads up about conditions.
The system itself “has been incrementally upgraded throughout the past several years,” going from hard-wired telecommunications between computers to a web-based system that’s “essentially a server farm that then shares all the information across everything,” said McCormick, managed airspace security for the FAA earlier in his career.
“The aviation system is a complex network of networks. So as the complexity has grown over time, as the technology has transferred from those hard-wired to those wireless systems, it causes greater chance that something could go wrong in that connectivity,” McCormick said.
Exactly what happened with this outage remains to be seen, he noted.
Transportation Secretary Pete Buttigieg said the outage has been fully restored, but he’s directed a review of the system and the root causes of the outage. “There is no evidence of a cyberattack at this point,” according to White House press secretary Karine Jean-Pierre.
McCormick said he’s still comfortable flying and the public should be comfortable too. He emphasized, “more likely than not,” this will not be a continuing problem.