Service trials of the MB.150 determined the aircraft to hold sufficient promise to warrant further work, leading to the adoption of an expanded and strengthened wing and a more refined Gnome-Rhone 14N-7 engine.

By the outbreak of the Second World War, around 120 aircraft had been delivered to the Armée de l'Air but most were not sufficiently equipped to be considered operational.

Amongst the various aviation companies who took interest in the specification, to which the potential for a large production order was attached, was French aircraft manufacturer Société des Avions Marcel Bloch.

[1] They designed an all-metal stressed skin monoplane, powered by a single 930 hp Gnome-Rhône 14Kfs radial engine and armed with a pair of wing-mounted Hispano-Suiza-built HS.404 cannon.

[1] Following the implementation of various modifications, consisting of a strengthened wing of greater area, revised undercarriage arrangement and the installation of a 701 kW (940 hp) Gnome-Rhone 14N-0 radial engine with a three-blade constant speed propeller, on 29 September 1937, the MB.150 finally conducted its maiden flight.

[1] Months later, the MB.150.01 was handed over to the Centre d'Essais du Materiel Aerien (CEMA) for service trials; during one such official test flight in December 1937, a maximum recorded speed of 434 km/h (269 mph) was attained.

[4] By this point, wider circumstances within France, such as the declining diplomatic situation between the European powers and the enactment of several urgent re-equipment programmes for the French Air Force, proved favourable for the MB.150.

[4] Specifically, on 15 March 1938, one such programme, referred to as Plan V, was adopted, calling for the near-unrealistic delivery of 940 modern fighter aircraft to the Air Force within the space of a year.

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 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.

[13] During the initial stage of the conflict, known as the Phoney War, very few engagements between the MB.152 and the aircraft of the Luftwaffe occurred; in this period, only a single kill of a Junkers Ju 88 was recorded.

[14] During the Battle of France, a mixture of MB.151s and MB.152s equipped nine Groupes de Chasse; the MB.152 was the most numerous aircraft remaining in service during the final weeks prior to the signing of the Armistice of 22 June 1940.

[15] They proved to be tough aircraft, able to withstand considerable battle damage, rapidly reach high speeds during a dive, and functioned well as a gunnery platform.

[17] In comparison with its French contemporaries, according to aviation author Michel Cristesco: "the MB.152 was the least successful in combat and the one that suffered the heaviest losses".

[16] By April 1941, the German Armistice Commission had agreed with a proposal to standardise the Vichy Air Force onto the Dewoitine D.520, resulting in all other single-engine fighters being phased out.

Chrisesco alleged that around 95 MB.152s were secretly modified during late 1941 – early 1942 with a rear-fuselage fuel tank, giving them the range to cross the Mediterranean Sea to freedom.

[19] Those that were delivered were still in the process of working up when the Greco-Italian War broke out, leading to the wider Balkan Campaign between the major European fighters.

During February 1943, a contract for delivery of 20 aircraft was signed, but this was vetoed by the German authorities, which by now had a controlling say within Vichy French politics.