Asiana Airlines San Francisco Airport
An Asiana Airlines Boeing 777 plane is seen in this aerial image after it crashed while landing at San Francisco International Airport Saturday. Reuters

Investigators have called into question the skills of the pilot for Asiana Airlines Flight 214, the Boeing 777 that crash-landed in San Francisco on Saturday, killing two Chinese teenagers.

According to Reuters, South Korean pilot Lee Guang-guk, along with three other pilots in the plane, was interviewed on Monday by National Transportation Safety Board investigators. The federal investigation revealed that Lee had spent only 43 hours flying the 777. During the flight, Lee was accompanied and trained by a more experienced deputy pilot, Lee Jung-min, who had more than 3,220 hours with the Boeing 777.

While Lee Guang-guk had clocked only a small number of hours on the Boeing 777, he was not an inexperienced pilot. Lee had just under 10,000 total flight hours with various other types of jets before he crashed on Saturday.

"He wasn't a novice,'' Les Westbrooks, a former commercial airline pilot and professor of aeronautical science at Embry-Riddle Aeronautical University in Daytona Beach, Fla., told USA Today. "He was new to this particular plane, but he was a very experienced pilot.''

The NTSB investigation also revealed the likely cause of the Asiana Airlines Flight 214 crash. As Lee attempted to make his first ever landing with the 777 at San Francisco International Airport, he let his landing speed drop far too low. The plane was coming in at 119 miles per hour, described as “significantly below” the target speed of 158 mph by the NTSB.

"It is the most fundamental thing that you learn in flying . . . to not get slow like this,'' Westbrooks explained to USA Today. "Once we get real slow, the flow of the air over the wings starts to break apart, and it doesn't flow over smoothly, and we start losing our lift.''

As the Boeing 777 came in too slow, Lee lost altitude. He soon lifted the plane’s nose in an attempt to regain some height, and inadvertently collided the plane’s tail wing with a seawall near the runway. In the wreck, two Chinese students, Ye Mengyuan and Wang Linjia, were killed while sitting in the plane’s tail section.

Reuters reports that one of the girls may have been hit by a firetruck after the crash.

"We have information and evidence to suggest that one of our fire apparatus came into contact with one of the victims at the scene,” San Francisco Fire Department chief Joanne Hayes White told Reuters. “We're working closely with the NTSB as they conduct their investigation, particularly on this aspect."

This is the first fatal accident to occur with a Boeing 777 since the plane entered service in 1995.