The fourth planned mission, Soyuz 25, was intended to visit the station in July 1977, however it was cancelled after fuel reserves aboard Salyut 5 dropped to a level at which the mission could not have been safely completed.
The fourth planned mission was intended to visit the station in July 1977. The fourth planned mission was Soyuz 25. It was cancelled. Fuel reserves aboard Salyut 5 dropped to a level at which the mission could not have been safely completed.