Production aircraft used several different types of engines, leading to various mark numbers being applied to the Vimy to distinguish between the emerging subtypes. The use of different engines was often because of availability; relatively few engines from Rolls-Royce Limited were used in the Vimy during 1918 owing to low output levels from that manufacturer, while other manufacturers also struggled to keep up with engine demand that year. At one point, there was considerable enthusiasm for powering the Vimy with American Liberty L-12 engines, because of their plentiful supply at the time; while specified for production aircraft all orders for the Liberty-equipped Vimy were terminated in January 1919 and no examples were ever completed. The BHP Puma was another engine that had been intended for use on the Vimy, but the Puma was cancelled without any aircraft being fitted with the engine.