It carried supplies for the EO-2 crew aboard Salyut 6, as well as equipment for conducting scientific research, and fuel for adjusting the station's orbit and performing manoeuvres.

The spacecraft were powered by chemical batteries, and could operate in free flight for up to three days, remaining docked to the station for up to thirty.

[3][4] Progress 3 was launched at 22:31:22 UTC on 7 August 1978, atop a Soyuz-U 11A511U carrier rocket flying from Site 31/6 at the Baikonur Cosmodrome in the Kazakh Soviet Socialist Republic.

[5] Following launch, Progress 3 was given the COSPAR designation 1978-077A, whilst NORAD assigned it the Satellite Catalog Number 10999.

Whilst Progress 3 was docked, Salyut 6 was manned by the EO-2 crew, consisting of cosmonauts Vladimir Kovalyonok and Aleksandr Ivanchenkov.