The Li-2 operated on a flight from Khorog to Stalinabad (now Dushanbe). The pilot deviated from the prescribed flight path when approaching the Yauza pass (4,885 metres) and observing clouds in the gorge. While flying 15 km north-west of Rushan it got caught by a strong katabatic wind and crashed some 75-100 metres below the ridge into the southern slope of the pass. The immediate cause of the crash is a collision with a rock due to insufficient flight altitude in mountainous terrain and an unexpected drop in altitude of the aircraft in downdrafts. The main cause of the disaster is the wrong decision by the crew commander to change the established flight route in the mountainous area in the difficult situation. Accompanying reasons – discrepancy between flight data of Li-2 aircraft to flight conditions on high-mountain routes (low practical ceiling, insufficient rate of climb when flying above 3000 m); lack of instructions for flights on Li-2 aircraft along this route.