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.