The National Transportation Safety Board has started an investigation. An NTSB team has been sent to San Francisco. Asiana CEO Yoon Young-Doo said "Currently we understand that there were no engine or mechanical problems." It is thought that the plane was too low when it was coming in to land and hit the seawall. The NTSB said that it looked like the pilots were flying too slowly while approaching the runway. The sound of the stick shaker (when the yoke vibrates to warn pilots that the plane may stall) could be heard about 4 seconds before the crash on the cockpit voice recorder. The crew tried a go-around 1.5 seconds before the plane hit the ground and the engines seemed to have worked fine.