The crew, commanded by Bykov V. T., was operating a Li-2 aircraft with tail number CCCP-Л4460 on a passenger flight from Irkutsk to Bodaybo with a stopover in Kirensk on April 23.

According to available information, the crew members, along with airport staff, began drinking alcoholic beverages at the hotel that night.

Despite the challenging weather conditions along the route, the crew began preparing for departure to Bodaybo at 6 a.m., and the airport manager authorized the flight at an altitude of 1 800 meters, i.e., in the clouds.

In the Mamy area, the pilots descended through a break in the clouds and then flew along the Vitim River at an altitude of 100 meters below the surrounding mountains.

The airliner periodically encountered snow charges, and turbulence increased, causing deformation of the fuselage and wing, with banks reaching 50 to 60 degrees.