Soyuz-U held the world record of highest launch rate in a year in 1979 with 47 flights until this was beaten by SpaceX's Falcon 9 in 2022.

This model featured an upgraded core with enhanced RD-117/118 engines to mitigate issues like in-flight vibration and combustion instability.

This variant, mainly used to transport crew and cargo to the Mir space station, last flew in 1995, after production of Syntin ended due to cost reasons.

Although the Soyuz-U was generally reliable, occasional failures occurred, most of them on launches of Zenit and Yantar reconnaissance satellites.

On June 18, 1987, a launch of a Resurs satellite from Plesetsk ended disastrously when the Blok D strap-on LOX turbopump disintegrated at T+6 seconds due to ingested debris.

The booster lifted and flew until T+20 seconds when the shutdown command was unblocked and terminated engine thrust, causing it to fall near LC-43/4 and severely damage it.

The October 2002 launch of a Foton satellite crashed near the pad at Plesetsk after the Blok D strap-on booster suffered an engine malfunction.

Investigation into the mishap found that the Blok D's hydrogen peroxide pump had stopped working due to ingested debris.

A Soyuz-U mission failed to launch Progress M-12M to the ISS on 24 August 2011, when the upper stage experienced a problem and broke up over Siberia.

[15] The modernized Soyuz 2 was introduced in 2004, adding several key enhancements, including improved engines along with digital flight control and telemetry systems, enabling launches from fixed platforms and the use of large payload fairings.

The analogue flight control systems of the Soyuz-U and FG limited the ability of the launch vehicle to adjust its trajectory in-flight, requiring that the rocket be "aimed" before takeoff by a complex rotating launchpad.

Long and wide payload fairings also introduced too much aerodynamic instability for the old analog system to handle, limiting the vehicle's potential to launch increasingly larger commercial satellites.

After several years of development, flight tests and concurrent use, the Soyuz 2 replaced the Soyuz-U in 2017 the Soyuz-FG in 2019, and launched its first crewed mission in 2020.