The Yakovlev Yak-40 operated on a domestic flight within the Soviet Union from Leningrad to Kirovograd with en route stops at Khmelnitskiy and Kiev. During the descent and approach to Kiev, the flight crew likely became incapacitated by carbon monoxide. Several check list items were not accomplished, among others setting the barometric altimeter to airfield pressure. The flight crew commenced the final approach prematurely and the aircraft impacted terrain on a tank training range near Gorenychi at a speed of 420 km/h and a vertical speed of 3 m/s. Probable cause: The likely cause of the disaster may be the loss of crew performance due to exposure to carbon monoxide and other toxic components. This led to the failure to perform a number of operations during the descent, including the failure to establish the barometric pressure of the aerodrome, which was also facilitated by the “overlap” in the communication of the controller with the crew. The result was a premature descent in the aircraft and its collision with the ground.