RER A
Type C units entered service when the western end of the RER A between and opened on 19 January 1970, and reached on 23 November 1971: type D units then reinforced the former when that line extended to Saint-Germain-en-Laye on 1 October 1972, displacing the trains. From 8 December 1977, the connection of RER A and B at , and the extension of RER A to Noisy-le-Grand – Mont d'Est allowed all MS 61 units, including the Type E and Ex units, to move between and operate on the two lines.