Aeroflot flight 8641 departed Leningrad-Pulkovo Airport at 09:01 local time. Destination of the flight was Kiev-Borispol Airport. Cruising altitude was 9000 m. The aircraft lost control and crashed from an altitude of FL300 following the failure of the horizontal stabilizer jackscrew due to fatigue. The crew completed pre-landing briefing and checks at 10:48. The flight was then cleared to descend to 7800 m. The crew confirmed this clearance. The descent was initiated and the horizontal stabilizer was trimmed nose down. It moved to +0.3ø until it suddenly instantaneously moved beyond the mechanical stop (+2ø). The aircraft pitched nose down and the flight crew were not able to regain control. An overload on the aircraft structure caused it to break up at an altitude of 5700 m. Conclusion: the cause of the disaster is a sharp spontaneous transfer of the stabilizer to a dive due to the disconnection of the screw pair of the stabilizer shift mechanism due to the almost complete wear of the nut thread. This led to acceleration and subsequent destruction of the aircraft in the air from the action of off-design aerodynamic loads.