Soyuz TM-5 launched on 1988 June 7 and arrived at Mir on June 9 carrying the second Bulgarian in space, Alexandrov (not to be confused with the Soviet cosmonaut of the same name). He became the first Bulgarian to reach a Soviet space station (Georgi Ivanov failed to reach Salyut 6 on Soyuz 33 in 1979—Alexandrov was his backup). Their launch had been advanced by 2 weeks late in the planning stages to improve lighting conditions for the Rozhen astronomical experiment.

On September 5 cosmonauts Lyakhov and Mohmand undocked from Mir. They jettisoned the orbital module and made ready for deorbit burn to return to Earth. During descent, the spacecraft experienced a computer software problem combined with a sensor problem.^[3] This caused their landing to be delayed by a full day. The Descent Module, where they spent this 24-hour period, had no sanitary facilities. Consequently, they soiled themselves. ^[4] They would not have been able to redock with Mir because they had discarded the docking system along with the orbital module.^[4] Reentry occurred as normal on September 7. Following this incident, the Soviets decided that on future missions, they would retain the orbital module until after deorbit burn, as they had done on the Soyuz Ferry flights.^[4]