There's been no indication, from verbal calls or mechanical issues, that an emergency was ever declared by pilots. Most airlines would require all four pilots to be present for the landing, the time when something is most likely to go wrong, experienced pilots said. In addition to the two pilots, a third was "monitoring" the landing from a jumpseat, while a fourth was in the rear of the cabin.
"If there are four pilots there, even if you are sitting on a jump seat, that's something you watch — the airspeed and the descent profile," said John Cox, a former US Airways pilot and former Air Line Pilots Association accident investigator.
The Air Line Pilots Association, the world's largest pilots union, criticized Hersman for fueling speculation that the crash is the result of pilot error before all the facts have been determined.
"The NTSB's release of incomplete, out-of-context information has fueled rampant speculation about the cause of the accident," the union said in a statement Tuesday. "The field phase of the investigation is barely three days old, and the pilots on the flight deck, at the controls of the aircraft, had little opportunity to provide vital information as to what exactly happened during the event before disclosing data recorded during the last moments of the flight. "
Hersman said the board was following its usual pattern of trying to be transparent by releasing information as it is known.
By Tuesday afternoon, NTSB interviews with three pilots were complete and the fourth was underway.
In addition, authorities were reviewing the initial rescue efforts after fire officials acknowledged that one of their trucks might have run over one of the two Chinese teenagers killed in the crash. The students, Wang Linjia and Ye Mengyuan, were part of a larger group headed for a Christian summer camp with dozens of classmates.
Asiana President Yoon Young-doo arrived in San Francisco from South Korea on Tuesday morning, fighting his way through a pack of journalists outside customs.
He met with and apologized to injured passengers, family members and survivors. But Yoon said he can't meet with the Asiana pilots because no outside contact with them is allowed until the investigation is completed.
More than 180 people aboard the plane went to hospitals with injuries. But remarkably, more than a third didn't even require hospitalization.
The passengers included 141 Chinese, 77 South Koreans, 64 Americans, three Canadians, three Indians, one Japanese, one Vietnamese and one person from France.
South Korea officials said 39 people remained hospitalized in seven different hospitals in San Francisco.
The flight originated in Shanghai, China, and stopped over in Seoul, South Korea, before making the nearly 11-hour trip to San Francisco.
Lowy reported from Washington, D.C. Associated Press writers Jason Dearen, Terry Collins, Paul Elias, Lisa Leff and Sudhin Thanawala in San Francisco and Hyung-jin Kim in Seoul also contributed to this report.