Yuri Gagarin and his flight instructor Vladimir Seryogin died when their MiG-15 went down near the town of Novoselovo, about 90km from Moscow.
The official findings reported Gagarin and Seryogin had maneuvered to avoid colliding with bird or other object, and as a result, entered a tailspin and plummeted to the ground.
Yuri Gagarin was just 34 years old.