SAN FRANCISCO -- As workers began clearing debris from a Korean Boeing 777 on a runway here and preparing to repave parts of it on Thursday night, five days after Asiana Flight 214 crashed on arrival, the National Transportation Safety Board began a meticulous reconstruction of the flight crew's inputs into the autopilot and other cockpit automation systems during the flight's final minutes.
The crew told investigators in interviews that they believed the autothrottles were on, which would have relieved them of managing the plane's speed, and left them with only its altitude and course to manage in the last moments of the flight, along with assorted other settings.
But some of the instructions that the crew gave the autopilot may have disabled the auto-throttles, experts said. For example, when air traffic controllers told the flight crew to make a broad left turn and descend, the crew could have moved the autopilot into a mode called "flight level change," which is abbreviated on the instrumentation as FLCH and which American pilots commonly pronounce as "flitch."
Americans who fly the 777 say that on their airplanes, in flitch mode, the auto throttle does not work.
The safety board has not provided much detail, but Deborah A. P. Hersman, its chairwoman, said investigators needed to "validate" the information they had, meaning reconstruct the state of the cockpit automation.
But, she said, when the aircraft was at 7,600 feet, at 11:20:55 a.m., a controller told the crew to turn left and descend to 3,000 feet. "This is the sort of thing they can use automation for," she said.
Autopilots can be programmed to handle turns to a certain compass heading, maintain a rate of climb or descent to a specified altitude, fly at a certain speed, or even land. But pilots could specify instructions not physically possible, with combinations of speed and altitude changes, for example. One area of inquiry for the board is exploring the logic of the automated system.
There are two broader issues. One, as Ms. Hersman pointed out, is that the pilots are supposed to closely monitor what the automated system is doing, or what they think it is doing, including maintenance of airspeed. Another is the possibility of overreliance on technology.
Najmedin Meshkati, an engineering professor at the University of Southern California and an expert on human performance, said that pilots' reliance on technology leads to atrophy of critical flying skills, "just like muscle atrophy."
The airport was operating the runway on visual flight rules, because part of the instrument landing system was out of service for construction work on the runway, and the crew, accustomed to automated landings, evidently had trouble with a manual one.
Some degree of automation is essential in planes that fly for 10 or 12 hours, or even more. But, Dr. Meshkati said, "We really need to refrain from irrational exuberance in embracing automation and new technology." He said that from what is known, the crash here last Saturday was in a category with the 2009 crash of Air France 447 in the equatorial Atlantic on a flight from Rio de Janeiro to Paris, which was due in part to mismanagement of automated systems.
Another area for inquiry is the adequacy of response by firefighters at the airport. Late Wednesday, the California Highway Patrol released 911 tapes of passengers calling in after the crash.
"We've been on the ground, I don't know, 20 minutes, a half-hour," one woman said. "There are people laying on the tarmac with critical injuries, head injuries. We're almost losing a woman here. We're trying to keep her alive."
The safety board said that based on video evidence, the first emergency truck arrived about two minutes after the crash, and firefighters began applying foam to the fire about a minute after that. They arrived in time to assist with the evacuation of passengers and crew.
The airport has not yet returned to normal operations, still lacking one runway, and passengers arriving on the parallel runway have had a good view of the wreckage.
The airport hopes to begin removing the burned-out wreckage of the Boeing 777 soon, and to re-open the runway on Sunday or Monday. About 100 flights a day have been canceled, and many are facing a a 45-minute delay.
This article originally appeared in The New York Times.