It is still not known exactly what the actual problem was, but it is often quoted as being a helium pressurization integrity test. The version of Soyuz 7K-OK spacecraft used for the missions carried a torus shaped docking electronics equipment housing surrounding the motor assembly on the back of the service module. This is thought to have been pressurized with helium to provide a benign environment for the electronics. It was then jettisoned after docking to lower the mass of the spacecraft for reentry. What went wrong with the electronics on all three spacecraft is still not known.
After 80 orbits of the Earth they landed on October 16, 1969, 180 km (110 mi) northwest of Karaganda, Kazakhstan.
The radio call sign of the spacecraft was Antey, referring to the Greek hero Antaeus, but more important, at the time of the flight, however, it was also the name of the largest practicable aircraft, the Soviet Antonov 22, made in Ukraine. But unlike the call signs of Soyuz 7 and Soyuz 8, this was not the name of a squadron in Soviet military training, of uncertain role, for the one that begins with the letter 'a' is Aktif, meaning Active.
Payloads are separated by bullets ( · ), launches by pipes ( | ). Manned flights are indicated in bold text. Uncatalogued launch failures are listed in italics. Payloads deployed from other spacecraft are denoted in brackets.