At 1.5 seconds before impact, there was a call from the crew to abort the landing.
The details confirmed what survivors and other witnesses said they saw: an aircraft that seemed to be flying too slowly just before its tail apparently clipped a seawall at the end of the runway and the nose slammed down.
Pilots normally try to land at the target speed, in this case 137 knots, plus an additional five more knots, said Bob Coffman, an American Airlines captain who has flown 777s. He said the briefing raises an important question: "Why was the plane going so slow?"
The plane's Pratt & Whitney engines were on idle and the pilots were flying under visual flight rules, Hersman said. Under visual flight procedures in the Boeing 777, a wide-body jet, the autopilot would typically have been turned off while the automatic throttle, which regulates speed, would been on until the plane had descended to 500 feet in altitude, Coffman said. At that point, pilots would normally check their airspeed before switching off the autothrottle to continue a "hand fly" approach, he said.
There was no indication in the discussions between the pilots and the air traffic controllers that there were problems with the aircraft.
The airline said Monday in Seoul that the pilot at the controls had little experience flying that type of plane and was landing one for the first time at that airport.
Asiana spokeswoman Lee Hyomin said that Lee Gang-guk was trying to get used to the 777 during Saturday's crash landing. She says the pilot had nearly 10,000 hours flying other planes but had only 43 hours on the 777.
Among the questions investigators are trying to answer was what, if any, role the deactivation of a ground-based landing guidance system due to airport construction played in the crash. Such systems help pilots land, especially at airports like San Francisco where fog can make landing challenging. The conditions Saturday were nearly perfect, with sunny skies and light winds.