The South Korean jetliner that smashed into the runway at San Francisco International Airport on Saturday was flying far too slowly to reach the runway and stalled when the pilot added power in a futile effort to abort the landing, the National Transportation Safety Board said Sunday.

The investigation into the crash of the Boeing 777 came to focus more sharply on possible pilot error Sunday as the president of Asiana Airlines ruled out a mechanical failure and federal investigators sought to interview the cockpit crew. Asiana Airlines spokesman Lee Hyomin said today the pilot in control of the Boeing 777 that crashed in San Francisco had little experience flying that type of plane and was landing one for the first time at the San Francisco airport. Hyomin said Monday 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.

“We’re not talking about a few knots here or there. It was significantly below the 137 knots” required for the approach, safety board Chairwoman Deborah Hersman said in describing data taken from the cockpit and flight data recorders. “We do hope to interview the crew members within the next few days.”

Hersman said the cockpit recorder revealed that seven seconds before impact there was a call to increase the plane’s speed. Three seconds later a “stick shaker” – a violent vibration of the control yoke intended to as a warning to the pilot – indicated the plane was about to stall. Just 1½ seconds later, a crew member called out to abort the landing.

Hersman said her agency was a long way – perhaps a matter of months – from reaching a conclusion on what caused the crash. But with Asiana insisting that there was no mechanical failure, the data from the flight recorders showing the plane far below appropriate speed and the fact that the pilots were flying a visual approach, the available evidence Sunday suggested the crew was at fault.

Hersman said the seven-year-old plane was equipped with current navigation tools to assist landings, including recent advances in GPS technology.

“A lot of this is not about the plane telling him, it’s about the pilot’s recognition of what’s going on ... to be able to assess what’s happening and make the right inputs to make sure they’re in a safe situation,” Hersman said. “That’s what we expect from pilots. We want to understand what happened in this situation.”

In Seoul, from where Flight 214 departed for the trans-Pacific flight with 307 people on board, the president of Asiana Airlines apologized Sunday for the crash.

“For now, we acknowledge that there were no problems caused by the 777-200 plane or engines,” Yoon Young-doo said at the company’s headquarters.

Flight 214’s pilots were Lee Jung Min, 49, a graduate of the Korea Aerospace University who joined Asiana in 1996, and Lee Kang Kuk, 46, who started his career at Asiana in 1994 and got his pilot’s license in 2001, South Korea’s Transport Ministry said in an emailed statement.

Chinese state media identified the two 16-year-olds who died in the crash as Ye Mengyuan and Wang Linjia, high school students from China’s eastern Zhejiang province. They were among a group of 70 students and teachers from three Chinese schools.

By Saturday night, all 307 on board the Asiana flight had been accounted for, authorities said. A total of 182 people had been transported to hospitals. Hospital officials said Sunday afternoon that the crash had left at least two people paralyzed with spinal injuries. Eight people remained in critical condition.

Investigators are trying to determine whether one of the victims was killed by a fire truck rather than by crash trauma, San Francisco Fire Chief Joanne Hayes-White said, according to the San Francisco Chronicle.

“Based on the injuries sustained, it could have been one of our vehicles that added to the injuries, or another vehicle,” Hayes-White told the newspaper. “That could have been something that happened in the chaos.”

Witnesses said that the plane’s tail struck the ground first and that the aircraft braked suddenly and spun around. They said the plane did not appear to catch fire until it came to a halt.

The plane’s tail snapped off on contact with the ground, suggesting that the pilot may have approached the runway with the plane’s nose higher than normal.

The runway begins at the edge of San Francisco Bay, separated from the water by a stone seawall. Debris from the plane was spread from the seawall along the runway to the spot where the plane came to a stop.

The tail fin, the two small tail wings that had been joined to it and landing gear were strewn on the runway, closer to the seawall than to the plane’s final location.

Thousands of passengers were stranded at San Francisco International Airport after Saturday’s crash, which shut down the airport’s four runways. The airport’s restaurants stayed open all night Saturday to cater to stranded travelers whose stood for hours in long lines to rebook their tickets.

Two runways reopened about three hours after the crash. Some international flights began leaving again Saturday night.

At about 1 p.m. Sunday, a third runway reopened, officials said on Twitter.

Asiana is South Korea’s second-largest carrier, after Korean Air. It has recently tried to expand its presence in the United States and joined the Star Alliance, which is anchored in the United States by United Airlines. Asiana has a fleet of 79 aircraft, including a dozen Boeing 777s. It flies to 23 countries and 71 cities.

Saturday’s accident was Asiana’s worst since 1993, when a Boeing 737 crashed in Mokpo, south of Seoul, killing 66 people, according to the National Archives of Korea.

Korean Air Lines’s crash history in the 1990s prompted the government to order its carriers to get new planes and pilots more training. Asiana’s accident may prompt a new round of similar measures.

“Asiana’s accident is going to damage the image of not just Asiana, but all Korean airlines,” said Um Kyung A, an analyst at Shinyoung Securities in Seoul. “It only takes one incident to undermine years of work Korean airlines have made to get a solid, accident-free record. This will prompt the government to call for stricter safety measures.”

Asiana was ranked among the top five global airlines by Skytrax in each of the past five years.

Korean Air, the country’s biggest carrier, in 2000 hired two executives who worked with U.S. airlines to help improve its safety standards after a slew of accidents, including a 1997 crash in Guam that killed 228 people. The accidents prompted the government to tighten safety standards at Korean airlines, as well as foreign ones flying into the country. It also strengthened regulations on pilot and maintenance licenses.

Pilots were required to be trained and evaluated at an international center, and airlines were required to fly more hours on domestic routes before obtaining a license to fly overseas. The government also strengthened safety regulations at domestic airports.

News wire services contributed to the report