The M.40 was an all-metal equal-span biplane powered by a 380hp (280kW)Fiat A.20 piston engine. It had a large central float with a stabilising float under each wing. The crew sat in tandem open cockpits and the M.40 was armed with one fixed and one movable 7.7mm (0.303in) machine-gun.[1] Two were built, given the serials MM.88 and MM.89, but following testing, the aircraft was not put into production.