SAN FRANCISCO -- Investigators trying to understand why Asiana Airlines Flight 214 crash-landed focused Monday on the actions of an experienced pilot learning his way around a new aircraft, fellow pilots who were supposed to be monitoring him, and why no one noticed that the plane was coming in too slow.
Authorities also reviewed the initial rescue efforts after fire officials acknowledged that one of their trucks may have run over one of the two Chinese teenagers killed in the San Francisco International Airport crash. The students were the only fatalities.
National Transportation Safety Board Chairman Deborah Hersman said investigators watched airport surveillance video to determine whether an emergency vehicle hit one of the students. But they have not reached any firm conclusions.
The NTSB also said part of the jet's tail section was found in San Francisco Bay, and debris from the seawall was carried several hundred feet down the runway, indicating that the plane hit the seawall on its approach.
Investigators have said Flight 214 was flying "significantly below" its target speed during approach when the crew tried to abort the landing just before the plane smashed onto the runway.
Authorities don't know whether the pilot's inexperience with the Boeing 777 and landing at San Francisco airport played a role.
Asiana spokeswoman Lee Hyomin said pilot Lee Gang-guk had logged nearly 10,000 hours operating other planes, but had only 43 hours in the 777, a plane she said he was still getting used to.
It's not unusual for veteran pilots to learn about new aircraft by flying with more experienced colleagues. Another pilot on the flight, Lee Jeong-min, had 12,390 hours of flying experience, including 3,220 hours on the 777, said South Korea's Ministry of Land, Infrastructure and Transport.
It was unclear whether the other two pilots were in the cockpit, which in the Boeing 777 typically seats four. But that would be standard at most airlines at the end of a long international flight.
NTSB lead investigator Bill English said pilot interviews were going slowly because of the need for translation.
Information gleaned from the Boeing 777's flight-data recorders revealed a jet that appeared to be descending normally until the last half-minute before impact. But something went wrong. The plane continued slowing to 118 knots (136 mph), well below its target speed of 137 knots (158 mph) that is typical for crossing the runway threshold. By that time, it had descended to just 200 feet.
Eight seconds later, with the speed still falling, Ms. Hersman said, the throttles were moved forward, an apparent attempt by the pilot to increase speed. But it was too little, too late. Five seconds later, at 50 percent power, speed began to increase.
A key question raised by the NTSB account is why two experienced pilots apparently didn't notice the plane's airspeed problem.
Part of the answer may lie in whether the pilot flying, after switching off the autopilot, still had the plane's autothrottle engaged during the descent. Aviation safety experts have long warned that overreliance on automation is contributing to an erosion of pilots' stick-and-rudder flying skills.
More than 180 people aboard the plane went to hospitals with injuries. But 305 of 307 passengers and crew survived, and more than a third didn't require hospitalization. Only a small number were badly hurt.
Three firefighters -- and two police officers without safety gear -- rushed onto the plane to help evacuate passengers, including one trapped under a collapsed bulkhead.
The two dead passengers were identified as 16-year-old students from China set to attend summer camp in California with dozens of classmates. One body was found on the tarmac, near where the plane's tail broke off when it slammed into the runway; the other was found on the plane's left side, about 30 feet from where the jetliner came to rest after it skidded down the runway.
The two teens killed were close friends and top students. Wang Linjia showed talent in physics and calligraphy; Ye Mengyuan was a champion gymnast who excelled in literature.
The flight originated in Shanghai, China, and stopped over in Seoul, South Korea, before making the San Francisco trip. NTSB investigators are also sure to examine whether pilot fatigue played a role in the accident, which occurred after a 10-hour nighttime flight. The accident occurred in late morning in San Francisco, but in Seoul, it was 3:37 a.m.