The pilot of the Asiana Airlines Boeing 777 jet that crash-landed in San Francisco was being trained on the long-range plane.
Lee Kang-kuk was the second most junior pilot of four on board the aircraft and had 43 hours' experience flying the long-range jet.
It was Mr Lee's first attempt to land the Boeing plane at San Francisco.
He had flown there 29 times previously on different types of aircraft, said South Korean transport ministry official Choi Seung-youn.
Earlier, the ministry said he had accumulated a total of 9,793 flying hours, including his 43 at the controls of the 777.
Two teenage Chinese girls on their way to summer camp in the US were killed.
More than 180 were injured in the crash, the first fatal accident involving the Boeing 777 since it entered service in 1995.
The airline Asiana said Mr Lee was in the pilot seat during the landing.
It was not clear whether the senior pilot, Lee Jung-min, who had clocked up 3,220 hours on the aircraft, had tried to take over to abort the landing.
"It's a training that is common in the global aviation industry. All responsibilities lie with the instructor captain," Yoon Young-doo, the president and CEO of the airline, told a news conference.
Information collected from the plane's cockpit voice recorder and flight data recorder indicated that there were no signs of trouble until seven seconds before impact, when the crew tried to accelerate.
A stall warning, in which the cockpit controls begin to shake, activated four seconds before impact, and the crew tried to abort the landing and initiate what is known as a "go around" manoeuvre 1.5 seconds before crashing, NTSB Chairwoman Deborah Hersman said.
"Air speed was significantly below the target air speed" of 137 knots, she said. The throttle was set at idle as the plane approached the airport and the engines appeared to respond normally when the crew tried to gain speed in the seconds before the crash, Ms Hersman added.
In a tragic new twist, the San Francisco Fire Department said that one of the Chinese teenagers may have been run over by an emergency vehicle as first responders scrambled to the scene.
"One of the deceased did have injuries consistent with those of having been run over by a vehicle," fire department spokeswoman Mindy Talmadge said.
The two, Ye Mengyuan and Wang Linjia, were classmates and friends from the same middle school in Quzhou, in the prosperous eastern coastal province of Zhejiang.
The charred hulk of the aircraft remains on the airport tarmac as flight operations gradually returned to normal.
Ms Hersman said it was too early to speculate on the cause of the crash.
The data recorders corroborated witness accounts and an amateur video indicated the plane came in too low, lifted its nose in an attempt to gain altitude, and then bounced violently along the tarmac after the rear of the aircraft clipped a seawall at the approach to the runway.
The Asiana flight was flying to San Francisco from Seoul with 291 passengers and 16 crew members on board.
Several large groups of Chinese students were among the passengers.