The spacecraft was launched on time at 20:53:06 UTC on 25 November 2013 from the Baikonur Cosmodrome in Kazakhstan.

[1] The Kurs-NA docking system was tested by Progress M-21M during a fly-by of the ISS on 28 November 2013.

[3] Progress M-21M delivers goods to the ISS, as fuel components, water, service equipment, equipment for scientific experiments, containers with food, and parcels for the crew.

On 13 March 2014, Progress M-21M was used to raise the orbit of the ISS by "two kilometers" after an engine burn of "almost ten minutes".

[4] Due to problems with the Kurs-NA docking system during the last test in November 2013, another test with the system was successfully done during a two-day free flying period in April 2014.