Two separate human errors caused a breakdown in radio communications that brought Southern California’s major airports to a near-stop Tuesday and led to at least five instances in which planes came too close, Federal Aviation Administration officials said.
“A loss of communication is a serious matter, and it should not have occurred,” Rick Day, a senior FAA official, said Wednesday.
On Tuesday, FAA officials had insisted that the more than three-hour system shutdown posed no safety risks. But they acknowledged Wednesday that they were investigating five incidents in which planes lost the required separation distance during the first 15 minutes of the communications breakdown.
In two cases, large airliners -- a UPS cargo plane and a Northwest Airlines flight bound for Southern California airports -- came much closer to small corporate jets than federal guidelines allow, requiring at least one pilot to take corrective action. FAA officials repeated Wednesday that they did not believe lives were ever at risk.
The agency’s radio system in Palmdale shut itself down Tuesday afternoon because a technician failed to reset an internal clock -- a routine maintenance procedure required every 30 days by the FAA. Then a backup system failed, also as a result of technician error, officials said.
The radar system in Palmdale, contrary to what some FAA and union officials had said Tuesday, did not shut down.
The radio system that crashed about 4:30 p.m. Tuesday at the Los Angeles Air Route Traffic Control Center in Palmdale is a high-tech touch-screen tool that allows air traffic controllers to quickly communicate with planes in transit. Controllers at the Palmdale facility communicate with cruise-altitude air traffic across Southern California and most of Arizona and Nevada, an area of about 178,000 square miles.
FAA officials said they had known for more than a year that a software glitch could shut down radio communications and were in the process of fixing it. In the meantime, they required manual resetting of the communications system -- a process they described as similar to rebooting a personal computer.
The problem so far has been corrected only in Seattle, one of 21 FAA regional air-traffic control centers that have used the system since the mid-1990s.
The radio failure rippled throughout the nation’s airports, grounding hundreds of commercial flights and forcing controllers working from other centers to divert hundreds more to locations outside Southern California.
Los Angeles International Airport officials said about 30,000 passengers were affected, with 500 or 600 spending the night in the terminals. The backlog of incoming flights was not cleared until 3 a.m. Wednesday. At LAX, 450 flights were diverted or canceled and another 150 were delayed. An additional 32 were canceled Wednesday morning because the aircraft did not arrive Tuesday night.
Other airports -- Ontario, Bob Hope, John Wayne, Long Beach and Palm Springs, as well as San Diego -- experienced significant delays, and airports throughout the West took diverted flights.
The computer glitch that snarled air traffic was first discovered more than a year ago in Atlanta after the FAA upgraded its computers.
“That’s why we built in strict maintenance procedures and protocols,” said FAA spokesman Greg Martin. He said his agency is aggressively pursuing the reason why the routine and simple procedure was skipped at the Palmdale air traffic center.
Tuesday’s communications failure marks the first time that the backup system has failed when the radio system shut down, Martin said.
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.
Hamid Ghaffari, a union official at the Palmdale facility, described a scene of high tension Tuesday evening as controllers tried to use personal cellphones to warn controllers at other facilities and watched close calls unfold without being able to alert the pilots.
Martin called the remarks “wildly overstated” and said “none of these incidents under our definition would be considered near midair collisions.”
Ghaffari said three controllers had filed job injury claims as a result of the stress, but said none of them would speak to the media.
“You can see planes getting close together, but you can’t talk to them,” said Ghaffari, describing conditions Tuesday evening.
“That’s what made it particularly harrowing.”
Once the Palmdale radio system failed, controllers at other FAA facilities, following contingency plans, took over communication with scores of airborne flights.
“En route aircraft were safely handed off to other air traffic control facilities, as designed,” Martin said.
Controllers said they believed at least two of the incidents were dangerous, and FAA officials acknowledged those two were the most serious.
“I can’t comprehend where the government can come out and say safety was never compromised,” said Ghaffari, whose union has long complained about being understaffed.
Ghaffari, who has reviewed the radar tapes, described the two incidents.
In one, he said a Citation jet headed northwest from Phoenix to Monterey and a UPS cargo jet headed southwest from Louisville to Orange County’s John Wayne Airport came within two miles of each other horizontally at 35,000 feet over Twentynine Palms. The vertical separation at that time was 100 feet.
Planes flying above 29,000 feet are required to be separated by nearly six miles horizontally and 2,000 feet vertically.
A spokesman for UPS confirmed that the pilot of Flight 1292 took evasive action after receiving an alert from the plane’s collision-avoidance system, but said the incident was not serious.
“The pilot received a warning and took minor corrective action,” said spokesman Mark Giuffre. “He climbed about 1,000 feet and they did see a business jet going by. The flight continued without event, but we are investigating it to find out what happened.”
In the other incident, Ghaffari said a chartered Gulfstream III jet headed east from Long Beach to Dulles airport near Washington, D.C., was climbing to 41,000 feet over Needles. It came within less than a mile horizontally of a Northwest Airlines jetliner that was headed southwest from Detroit to San Diego at 39,000 feet.
The radar indicates that the Gulfstream halted its climb momentarily, possibly in an evasive action. The pilot of the Gulfstream leveled off about 900 feet the below Northwest Flight 277, Ghaffari said, to avoid coming any closer.
“They practically went right over one another,” he said.
But Northwest spokeswoman Mary Stanik said there were no reports of problems on Flight 277. “All there was was a delayed descent to San Diego,” she said.
Of the three other incidents, FAA officials said one involved a passenger jetliner and two involved cargo jets. They provided no additional information, other than to say one incident involved separation that was only slightly below the required 5 3/4 miles.
Officials from Professional Airways Systems Specialists, the union that represents FAA technicians, acknowledged Wednesday that an improperly trained employee failed to reset the Palmdale radio system.
But they said the quirk in the system, known as Voice Switching and Control System, is a “design anomaly” that should have been corrected after it was discovered last year in Atlanta.
As originally designed, the VSCS system used computers that ran on an operating system known as Unix, said Ray Baggett, vice president for the union’s western region.
The VSCS system was built for the FAA by Harris Corp. of Melbourne, Fla., at a cost of more than $1.5 billion.
When the system was upgraded about a year ago, the original computers were replaced by Dell computers using Microsoft software. Baggett said the Microsoft software contained an internal clock designed to shut the system down after 49.7 days to prevent it from becoming overloaded with data.
Software analysts say a shutdown mechanism is preferable to allowing an overloaded system to keep running and potentially give controllers wrong information about flights.
Richard Riggs, an advisor to the technicians union, said the FAA had been planning to fix the program for some time. “They should have done it before they fielded the system,” he said.
To prevent a reoccurrence of the problem before the software glitch is fixed, Laura Brown, an FAA spokeswoman, said the agency plans to install a system that would issue a warning well before shutdown.
Martin, the chief FAA spokesman in Washington, said the failure was not an indication of the reliability of the radio communications system itself, which he described as “nearly perfect.”
Times staff writers Megan Garvey and Andrew Blankstein contributed to this report.