Noting that some witnesses reported hearing the plane's engines rev up just before the crash, Barr said that would be consistent with a pilot who realized at the last minute that the plane was too low and was increasing power to the engines to try to increase altitude.
Barr said he could think of no reason why a plane would come in to land that low.
"When you heard that explosion, that loud boom and you saw the black smoke ... you just thought, my god, everybody in there is gone," said Ki Siadatan, who lives a few miles away from the airport and watched the plane's "wobbly" and "a little bit out of control" approach from his balcony.
"My initial reaction was I don't see how anyone could have made it," he said.
Inside the plane, Singh, who was sitting in the middle of the aircraft with his family, said there was no forewarning from the pilot or any crew members before the plane touched down hard and he heard a loud sound.
"We knew something was horrible wrong," said a visibly shaken Singh. He said the plane went silent before people tried to get out anyway they could. His 15-year-old son said luggage tumbled from the overhead bins.
Passenger Benjamin Levy said it looked to him that the plane was flying too low and too close to the bay as it approached the runway. Levy, who was sitting in an emergency exit row, said he felt the pilot try to lift the jet up before it crashed.
He said he thought the maneuver might have saved some lives. "Everybody was screaming. I was trying to usher them out," he recalled of the first seconds after the landing. "I said: 'Stay calm, stop screaming, help each other out, don't push.'"
By the time the flames were out, much of the top of the fuselage had burned away. The tail section was gone, with pieces of it scattered across the beginning of the runway. One engine appeared to have broken away.
The flight originated in Shanghai, China, and stopped over in Seoul, South Korea, before making the nearly 11-hour trip to San Francisco, airport officials said. The airline said there were 16 crew members aboard and 291 passengers. Thirty of the passengers were children.