Pilots of the Asiana Airlines flight that crashed in San Francisco have told U.S. investigators they thought the plane's autothrottle was maintaining proper landing speed but it wasn't.  

In the first description of interviews with the crew of the Boeing 777, U.S. National Transportation Safety Board Chairwoman Deborah Hersman cited the pilots as saying that they thought the correct speed was set and did not realize they were going too slow until seconds before impact.

The pilots said in interviews that as they prepared to land, they set the autothrottle, which is used to control the engines to maintain safe airspeed, at the recommended 254 kilometers per hour but speed fell to unsafe levels.

The pilots also told U.S. investigators that at 152 meters in altitude, they noticed the plane was not maintaining speed and flying too low and slow.

They said they tried to increase engine power for the airplane to go around for another landing attempt but it was too late and the plane crashed onto the runway.