Pulkovo flight 612 departed Anapa (AAQ) for St. Petersburg (LED) at 15:05. The Tu-154M climbed to the cruise altitude of 35,100 feet (10.700 m). Because of storm cells ahead, the pilot decided to change course laterally by 20 km and attempted to climb over the storm cells. However, the thunderstorm front was unusually high, extending up to 15 km (49,000 feet). The Tu-154 entered an area of severe turbulence, pushing up the airplane from 11.961 m to 12.794 m within just 10 seconds. The angle of attack increased to 46 degrees and the airspeed dropped to zero. It entered a deep stall from which the crew could not recover. The plane crashed and burned in a field. The cause of the crash was the loss of control in the manual flight mode with supercritical angles of attack, causing a stall with the subsequent transition to a flat spin and collision with the ground with a large vertical velocity. Factors were considered poor crew coordination, and failure to follow the instructions in the Aeroplane Flight Manual to prevent a stall. Also, the crew training methods used were insufficient to demonstrate the dangers of manual flight at high altitudes.