were manufactured at Châteauroux, Berry while the other half were built at Bordeaux–Merignac, Nouvelle-Aquitaine. From January 1940 onwards, production was centered at Châteauroux alone. During December 1938, the first of the pre-production aircraft were completed; on 7 March 1939, the first production fighter was delivered to the French Air Force. By mid-May 1939, only 22 aircraft, a combination of MB.151s and MB.152s, had been dispatched; of these, only 10 had been accepted by the Air Force. The MB.153 and MB.154 were intended as testbeds for American engines but only the MB.153 flew and when it crashed a few days later as damaged beyond repair, pursuit of these alternatives also ceased. Attention shifted to extending the range of the MB.152 by moving the cockpit aft to make room for a new fuel tank; other modifications included a slightly broader wing and revised aerodynamics around the cowling. The resulting MB.155, performed favourably in flight tests and was ordered into production in 1940 but only 10 aircraft had been completed by the Fall of France. Under the terms of the armistice, the remaining 25 on the production line were completed and delivered into Vichy service. From there, some eventually made their way into the Luftwaffe after 1942. The final member of the family, the MB.157 had a far more powerful engine and eventually became a very different aircraft as the design evolved from the MB.152 to accommodate the larger and heavier 1,590 hp Gnome-Rhône 14R-4 motor. Unfinished at the time of the armistice, it was ordered to be completed and flown under German supervision. Demonstrating superb performance, it was taken to Orly where the power plant was removed for testing within a wind tunnel. The excellence in the design was confirmed by Germans when they completed and tested it in 1942, reaching up to flat speed. It was later destroyed in an Allied air raid. Operational history Upon evaluation, early deliveries were deemed unsuitable for combat operations, principally due to issues with the tailplane; thus, plans were laid for the first 157 production fighters to be stored awaiting modification, while additional production examples were built with the correction made. Furthermore, the type was initially confined to performing training duties alone; prior to the outbreak of the Second World War, only a single squadron, allocated to the 1st Escadre de Chasse, received the type. Upon the eve of the conflict, around 249 aircraft had