What happened in the final minutes of Asiana Flight 214 before it crashed on runway 28L at San Francisco International Airport?
It's the primary question investigators with the National Transportation Safety Board are asking as they debrief the pilot at the controls of Asiana 214.
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"What we do know is that we have an experienced pilot. He has a lot of hours, but he is new to the 777," said Deborah Hersman, chairwoman of the NTSB. "We need to understand what that transition training looks like and the initial operating experience, which is what he was doing. Getting time in the aircraft with an experienced instructor."
As of Tuesday morning, the NTSB had interviewed two of the four pilots.
Was He Warned of a Stall?
One piece of information the NTSB has yet to release is the transcript of what was on the cockpit voice recorder for Asiana 214. The CVR records all communication between pilots and the air traffic controllers and between pilots in the cockpit.
Was Lee Gang-guk, the pilot at the controls, warned by the other pilot in the cockpit that he was flying too low and too slow to make the runway?
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It's a main question Hersman and her staff are focused on.
The NTSB said Lee had slowed the Boeing 777 to a point that the plane issued a warning of an impending stall. The target air speed for landing the 777 at San Francisco International Airport is 137 knots. Asiana 214 slowed down to 103 knots just before its tail hit the seawall and the plane tumbled down the runway.
Experience With 777
Another focus is whether Lee's lack of experience in the 777 lead to the crash. The Asiana pilot had just 43 hours at the controls and was still in the process of getting certified as a captain on the plane, a process that requires 60 hours flight time.
"We are taking a look through all those records. Those records have been provided to us through Asiana and we expect to brief others on that this afternoon," said Hersman.
—By CNBC's Phil LeBeau; Follow him on Twitter: @Lebeaucarnews