In its heyday, the 1950s and 1960s, the Ae 6/6 was the Gotthard locomotive par excellence, both for passenger and freight traffic. They were also used on the route through the Simplon tunnel. They were used in turns to ensure regular servicing in the main maintenance facility at Bellinzona. In the late 1960s, the two prototypes were retired from service on the Gotthard line; gradually followed by the rest of the class, although occasional workings continue to this day. After the introduction of the Re 6/6 locomotives, most Ae6/6 were reallocated to services in the Swiss plateau. Since this time, they have been mostly used for freight trains, because they are too slow for the faster passenger services. An exception were those units hired by the BLS, which were sometimes used to haul relief and intercity trains over the Lötschberg route.