A Pan American World Airways jetliner and a United Express commuter jet nearly collided in cloudy skies near Los Angeles International Airport before taking evasive action at the direction of air traffic controllers, aviation officials said Thursday.
"It was as close as I've ever seen them get," said Karl Grundmann, a controller who watched Tuesday's incident unfold on radar screens at the Los Angeles Terminal Radar Approach Control center.
Because of the overcast, no one on the ground or in either plane saw how close the jets came to each other, but Grundmann estimated that it could have been as little as 300 feet.
Elly Brekke, a spokeswoman for the Federal Aviation Administration, which employs the controllers, said preliminary readouts of taped data from the radar systems indicate that the planes came within about half a mile of each other horizontally and about 300 feet vertically.
FAA rules require at least 1,000 feet of vertical separation and/or three miles of horizontal separation.
The incident occurred shortly after noon over Santa Monica Bay, about 12 miles west of the airport, according to controllers.
The FAA said the Pan Am jet, Flight 2441 from San Francisco, was approaching LAX for a landing as the commuter plane was climbing after takeoff.
According to Grundmann, a safety committee chairman for the National Air Traffic Controllers Assn., the Pan Am jet had been assigned an altitude of 10,000 feet, while the United Express plane had been told to climb to 9,000 feet.
"But the (Pan Am) guy descended through his assigned altitude," Grundmann said. "All of a sudden, the controller handling that sector said, '(Pan Am) Clipper descending through 10.' He said it loudly, so all the other controllers could hear it. . . .
"The controller handling the United Express told his plane to descend immediately, while the controller handling the Clipper told his plane to climb," Grundmann continued. "As we watched, the two targets merged on the screen. The altitude readouts were almost the same. . . .
"We all held our breath for a minute, and then they came apart again," he said. "There was a sigh of relief. And a lot of congratulations for the two guys who got 'em apart."
Brekke said the controller who shouted the warning apparently was prompted by an automatic "conflict alert" system that sounds an alarm, flashes a warning on the radar screen and highlights the planes involved.
Since neither pilot filed a report--apparently because neither saw the other plane in the overcast--the incident is being listed officially as a "pilot deviation" rather than a "near miss," Brekke said. The matter is under investigation by the FAA, officials said.
While the FAA identified the United Express plane as Flight 920, United Express officials said no such flight number exists and no flight with any similar number was scheduled to take off from LAX on Tuesday.
"The FAA has told us that one of our planes was involved--a BAE 146 (90-passenger jet)--but we have been unable to confirm that," said Mark Peterson, a vice president of the Fresno-based line. "We don't know what flight that might have been."