The Federal Aviation Administration (FAA) has not yet been able to determine what caused a significant malfunction in a computer system that routes air traffic over the sky above Washington, D.C., causing hundreds of flights to be delayed and cancelled Saturday.

The glitch, which centered on systems in an air traffic control station in Leesburg, Virginia, caused the cancellation of more than 440 flights for hours and caused hundreds of other flights to be delayed.

The FAA said it was working with carriers to resume normal service and that the problem "had nothing to do with an accident or hacking," Reuters reported. It blamed “technical issues” and “automation issues” for the problem but was unable to specify what they were.

“The FAA is continuing its root cause analysis to determine what caused the problem and is working closely with the airlines to minimize impacts to travelers,” the agency said in a tweet.

Information posted online by the FAA indicated there was a problem with the En Route Automation Modernization computer system, also known as ERAM, at the Leesburg center, the Associated Press reported.

The FAA finished installing the system in the last of 20 high-altitude traffic control centers earlier this year. The completion was years behind schedule and the system has suffered from problems, the AP added.

Many passengers complained that authorities had left them in the dark, noting that the FAA posted no information about the problem on Twitter until 4:30 p.m. — after it had been fixed.

“The airline was saying, ‘It’s not our fault; it’s the airport,’ and the airport said, ‘It’s not our fault; it’s the FAA,’ but you go to their Twitter account and they [FAA officials] haven’t said anything about it,” Ilya Lozovsky, who had been waiting for more than seven hours at Dulles International Airport for his flight, told the Washington Post Saturday.

While flights have been operating as normal since Saturday afternoon, media outlets reported that it would likely take airlines until Sunday to clear the full backlog of delayed passengers.