The Tu-154 (CCCP-85311) was operating the first leg of flight 5143 from Karshi to Leningrad, with a scheduled stopover at Ufa, piloted by the crew of the 219th flight squadron, consisting of commander O. P. Belisov (48), co-pilot A. T. Pozyumsky (48), flight engineer A. S. Mansurov (32), navigator G. N. Argeev (41), with 5 flight attendants onboard the flight. There were 191 passengers onboard the flight, which had consisted of 139 and 52 children, which met the standard regulations of 92,200 kg (92.2 tonnes). The aircraft took off at 23:00 PM (4 hours behind the scheduled departure of 19:00 PM); the temperature of Karshi Airport was 33°C (91.4°F). The Tu-154 climbed altitude, following the guidelines of the Aircraft Flight Manual (AFM).

The aircraft gained an altitude of 11,600 meters (38,000 ft) at a speed of 400 km/h (215 kts). The crew had changed the autopilot to gain speed, leading the aircraft to pitch down. The crew pulled the aircraft up, making the Tu-154 on the verge of activating the alarm of the critical angle of attack; suddenly, the alarm had stopped due to a blown fuse. The aircraft then entered the jet flow zone with a weight of 86,500 kg (86.5 tonnes); the air temperature of the specified flight path was 16.5°C (61.7°F) higher than the standard. The Tu-154 suddenly entered a critical angle of attack. This led to disruption in the airflow to the engines, leading to shaking; the flight engineer thought it was a compressor stall and ordered the crew to decrease the speed.

Instead of pushing back the throttle, they both decreased and increased the speed of the aircraft. The captain still continued to hold the altitude. The aircraft had then repeatedly had critical angles of attack; as a result, the engines failed, causing the aircraft’s speed to decrease 290 km/h (160 kts) after 1 minute and 17 seconds after the repeated angles of attack, leading the aircraft to lose control and enter a flat spin.