Beryozovsky District, Krasnoyarsk Krai, Russia: A Tupolev Tu-104 from the Aeroflot Airline, registration SSSR-42370, disappears from radar after some troubling and confusing reports from the cabin crew. Traffic controllers reported a chaotic cabin and a strange background noise before the end of transmission from the Russian jetliner. The Tupolev was on a flight from Khabarovsk to Moscow with two intermediate stops, one in Irkutsk.
Soon, after the takeoff from Irkutsk, the pilots made a preliminary call to Krasnoyarsk air traffic control (ATC) and got clearance to enter the airspace. A few minutes later, controllers reported an incoherent emergency call from the Tupolev cabin crew. Controllers also reported a strange background noise that they could not identify. Moments later, all of their hails to the Tupolev went unanswered and emergency crews were dispatched to the scene.
Investigators soon discovered that the plane impacted the ground in an inverted (cabin side down) position and at a relatively severe angle of around 40 degrees. Investigators concluded that the plane came down from disorientation of the pilots in the cloud cover, but further investigation revealed a strange substance on the left side of the fuselage, a propellant that should not have been there. Later findings show that the propellant was used in an anti-aircraft missile that the Krasnoyarsk defense force used regularly. Officials of the krai later admitted to an error in a military training exercise that let the missile lock on to the Tupolev, which impacted the airliner. Officials later correlated the strange sound heard on the voice transmissions as that of the missile system closing on the plane. With 76 passengers and 8 crew, the crash marked the worst aviation disaster in Russia at that time.