On the afternoon of the crash, the NTSB launched an investigation in search for a probable cause. Over the next three months, they conducted 349 interviews, and collected and reconstructed pieces of the aircraft. The Airbus A300 took off shortly after a JAL Boeing 747-400 using the same runway. It flew into the larger jet's wake, an area of turbulent air. The first officer attempted to stabilize the aircraft with alternating aggressive rudder inputs. The force of the air flowing against the moving rudder stressed the aircraft's vertical stabilizer, and eventually snapped it off entirely, causing the aircraft to lose control and crash. The NTSB concluded that the enormous stress on the vertical stabilizer was due to the first officer's "unnecessary and excessive" rudder inputs, and not the wake turbulence caused by the 747. The NTSB further stated, "if the first officer had stopped making additional inputs, the aircraft would have stabilized". Contributing factors were characteristics of the Airbus A300-600's sensitive rudder system design and elements of the American Airlines Advanced Aircraft Maneuvering Training Program.