Sources are saying it was a Cold War era U2 spy plane that shut down the ATC Center in Palmdale, California on Wednesday afternoon.
The US Air Force flies U2s from Edwards Air Force Base in nearby Mojave, California. NBC News reports that it may have been one of these planes that may have fried the system for a couple of hours, causing delays for all flights heading to and from Southern California for the rest of the day.
The plane supposedly passed through the air space monitored by the ATC center at about 60,000 feet in altitude, causing the computers to struggle with keeping the plane colliding with commercial air traffic, though the air traffic would have been at least 20,000 feet below it. Calling it a "glitch" would be a big understatement.