When were the AC coaches introduced in the Indian Railways?

Furthermore to what the other answerer said already, I'd like to highlight some more points. In 1956, the first set of fully air-conditioned trains were introduced between Delhi-Howrah, and Delhi - Mumbai, as the AC express. read more

The North-Western Railway introduced air-conditioned stock in the late 1930's (the earliest was probably the Frontier Mail in 1936 or 1937). BBCI Railways also experimented with air-conditioning at about the same time. By the early 1950's, air-conditioning was available on several long-distance trains. read more

Fans and lights were mandated for all compartments in all passenger classes in 1951, and sleeping accommodations were introduced in coaches. In 1956, the first fully air-conditioned train was introduced between Howrah and Delhi. read more