In May 1937, the French Air Ministry placed an order with Société des Avions Marcel Bloch for two prototype floatplanes intended to fulfill a French Navy requirement for a twin-engined torpedo-bomber/reconnaissance floatplane.
[1] It was powered by two 1,060 hp (791 kW) Gnome-Rhône 14N radial engines and carried a crew of five.
[2] The first prototype made its maiden flight from Étang de Berre in June 1939.
[3] Although testing was relatively successful, the French Navy had meanwhile decided that the torpedo-bomber reconnaissance role could be better met by landplanes, with the much faster Lioré et Olivier LeO 451, already on order as a medium bomber for the French Air Force, being chosen.
On 9 September 1939, Bloch was told to suspend development trials, while on 10 December it was officially announced that no orders would be placed for either the MB.480 or its two competitors, the SNCAC NC-410 and the Loire-Nieuport 10.