During the communist period the 'M3' was the Gara de Nord - Dristor 2 section of what is today the M1.

[3] Construction work on another branch, from Nicolae Grigorescu to Anghel Saligny (at time named Leontin Sălăjan and Linia de Centură), began in 1988, but the work was halted in 1996 and the tunnels were flooded.

[4] Due to the very large gap between Pacii and Lujerului (then known as Armata Poporului) construction of Gorjului started.

In 2008, the long-overdue section from Nicolae Grigorescu to Linia de Centură, for which construction works resumed in 2004, was finally opened, also as a shuttle, as an extension of the M4.

[4] Because a line composed of two unconnected shuttles was very impractical, on 4 July 2009 the two branches from Preciziei and Anghel Saligny were linked sharing tracks with the M1 between Eroilor and Nicolae Grigorescu and thus forming the M3 as it is operated today.