The article aims to consolidate information regarding flight development tests of the 8K99 missile at the 53rd field research facility of the USSR Ministry of Defense (Archangelsk Region, Mirnyj). Besides official and technical documentation, archive papers of testing military units and test participants’ memories are used. The ocean-spanning missile 8K99 was developed in the Yuzhnoe Design Office (Dnepropetrovsk City) during the first half of the 1960s . It was intended for combat use within the Strategic Missile Forces as part of mobile and fixed missile systems. For the flight development tests of the 8K99 missile, there was built an experimental testing base (including technical and missile launch sites, command, measurement and computer complexes, etc.) and infrastructure facilities (roads, bridges), prepared drop areas for separated missile’s parts along its motion path and training target areas, set up testing military units, and trained engineering and technical personnel. During 1967-69, there were carried out flight development tests of the 8K99 missile as a part of the 15П699 mobile ground missile system. Despite overall positive results, the missile’s tests were discontinued. The 8К99 missile was not accepted for service, but its creation contributed to the development of national missilery. A set of ingenious engineering solutions are being used up to now in developing ocean-spanning missiles and space rockets. During flight development tests, testing military units’ personnel gained experience in operating complicated, dangerous, and sensitive systems