What happened
While en route to Leningrad, a military aircraft encountered poor weather conditions after passing Valday. During this phase of flight, it collided with another Soviet Air Force U-2 registered 51. The second aircraft was carrying one pilot. Following the mid-air impact, both airplanes lost control and dove into the ground. The wreckage came to rest approximately 15 km west of Valday. Both airframes were destroyed in the crash, and all three occupants across the two aircraft were killed.
Findings
Official investigations determined that the collision occurred because both aircraft were flying without any navigation or position lights illuminated. This operational decision was made to avoid detection by potential enemy forces during the flight.