With the development of the new Type 244 engine, ALCO introduced the FA freight locomotive in addition to the PA passenger locomotive in 1946. Not only did the propulsion electrics come from General Electric, the streamlined and modern design of the car body also came from Ray Patten, head of GE's design department. The FA got the twelve-cylinder engine and stood on two two-axle trucks. What all PA and FA have in common is that black smoke came out when accelerating due to the lack of air in the turbo lag.
The first FA-1 and FB-1 were built with 1,500 hp, but the later models and the FA-2 and FB-2 were built with 1,600 hp and also many of the first ones were upgraded. From 1950, they were also offered as FPA-2 and FPB-2, which were suited for freight and passenger service and had a steam generator. The last 34 FPA-4 and 12 FPB-4 built at Montreal for Canadian National in 1958 and 1959 got the new 251 engine with 1,800 hp.
In total, 1,397 units of the FA and FB series had been built when production ended in 1959. Among these were 23 FCA-3 which had been built for Pakistan. They were lighter, but had an A1A-A1A wheel arrangement to reduce the axle load. The “World Locomotive” DL-500 was based on the FA-2 and later on the PFA-4. It was built in B-B, C-C and A1A-A1A variants and exported into countries all around the world. Many survived into the 21st century.