Federal aviation officials plan to send a team to the Palmdale air traffic control center to investigate why a technician failed to perform required maintenance on a radio communications system, causing it to crash Tuesday and snarl flights across the country.
The shutdown, which lasted more than three hours, led to at least five instances in which planes came too close to one another and caused about 800 flights in and out of Southern California's airports to be canceled, delayed or diverted.
Laura Brown, a Federal Aviation Administration spokeswoman, said the team will arrive in the "next few days" at the Los Angeles Air Route Traffic Control Center in Palmdale, which tracks cruise-altitude air traffic across Southern California and most of Arizona and Nevada.
The FAA will try to determine why an agency technician failed to reset the radio system's internal clock -- a routine maintenance procedure required every 30 days by the FAA. The team will also review why a backup system was configured incorrectly, which caused it to fail.
The backup's failure left controllers with no way to communicate with other FAA centers or the high-altitude flights displayed on their radar screens, forcing them to hand flights off to other FAA facilities in the West.
The system, known as the Voice Switching and Control System, is a high-tech touch-screen tool that allows air traffic controllers to quickly communicate with planes in transit. It was installed in the nation's 21 air traffic control centers in the mid-1990s,
After the FAA upgraded its computers a year ago, it discovered that, if the radio system was not periodically reset, a software glitch caused it to shut itself down.
The FAA plans to roll out a fix, which will prevent the system from shutting down automatically, at 20 air traffic control centers in the next month, Brown said. The fix is being tested at a center in Seattle.
The technicians' union criticized the FAA on Thursday, saying that the agency did not adequately test the upgraded version of the radio system before it installed it in air traffic control centers across the country.
The union expects the technician who worked on the Palmdale system to be disciplined, even though he did not receive adequate training from the FAA, said Tom Brantley, national president of Professional Airways Systems Specialists.
"We've seen some behind-the-scenes e-mail traffic where the agency has assured members of Congress that the employee and the employee's supervisor would be held accountable," Brantley said.
The FAA said it was awaiting the outcome of the investigation to determine what disciplinary action, if any, it would take against the technician.
The Palmdale center was asked by FAA headquarters on Thursday to come up with a "lessons learned" plan from the outage, said Hamid Ghaffari, a union official at the facility.
Ghaffari said three controllers who filed job injury claims as a result of stress after the Tuesday incident have returned to work.