[2] Although a sturdy and highly manoeuvrable fighter aircraft,[3] it was considered underpowered and weakly armed when compared to its contemporaries and the M.S.406 was outperformed by the Messerschmitt Bf 109E during the Battle of France.

[2] The MS.405 was a low-wing monoplane of mixed construction, with fabric-covered wooden tail, with a bonded metal–wood material (Plymax) skin fixed to duralumin tubing.

Morane-Saulnier had a long history of producing warplanes dating back to the pre-First World War years but in the inter-war period, they had concentrated on civil designs.

[8][2] First flown by French aerobatic pilot Michel Détroyat, the prototype demonstrated the type's favourable flying characteristics from the onset.

[2] After 80 hours of test flights, in January 1936, the prototype was delivered with all military equipment fitted to CEMA at Villacoublay to participate in service trials.

[9] Development of the M.S.405 proceeded fairly slowly; testing revealed the need to modify the wing planform and dihedral, while the Chauvière-built propeller was replaced by a Levasseur-built counterpart.

[10] During March 1937, having been suitably impressed with its performance, an initial order was placed for the construction of 16 pre-production prototypes, which were to incorporate the design improvements that had been made upon the previous version.

[10] The cockpit had a modified windscreen to accommodate a new reflector sight arrangement, as well the adoption of electropneumatic controls of the armaments and provisions for the carriage of under-wing auxiliary fuel tanks.

[10] Following the completion of a pair of prototypes, during February 1940, the French government issued an order authorising the bulk upgrading of 500 M.S.406 fighters to the better armed, stronger and faster (509 km/h (316 mph) M.S.410 configuration.

[10] It took 15 days to convert each fighter but conversions were stopped in May 1940 to put every available combat aircraft into action during the Battle of France against invading German forces.

[14] On 23 August 1939, in response to the diplomatic crisis emerging over the Invasion of Poland, all French Air Force units were mobilised as part of preparations to be ready for imminent combat operations.

[15] Various M.S.406-equipped units were deployed along the border with Germany stretching between Luxembourg and Switzerland, intended to support the sizable ground elements of the French Army from the air.

During the Phoney War opening phase of the Second World War, a time of relatively low combat intensity, the type's activities focused upon air defence operations with the aim of countering the prolific aerial reconnaissance and probing activities of small groups of Axis-aligned fighters coming over the border, in addition to escorting friendly reconnaissance aircraft.

According to Botquin, by this stage, the weaknesses of the M.S.406 were already apparent, such as the lack of armouring, frequent gun-jamming, inadequate firepower, slow responsiveness of the guns, unreliable radio units, very high rate of engine wear, corrosion of rudder components, cabin glazing breaking under air pressure during certain manoeuvres, loss of exterior panels due to screws deteriorating rapidly, and the lack of rear-view mirrors.

[15] While the aircraft was very manoeuvrable and could withstand high amounts of battle damage, potentially giving possible advantages during combat against Luftwaffe fighters, the M.S.406 was overall outclassed by the Bf 109.

[20] The M.S.406 holds the unfortunate distinction of being the least effective French fighter in service during the Battle of France, which Botquin suggests was due to its relatively low firepower.

[4] Botquin stated of the aircraft: "it would be pointless to pretend, as was often done during the war for propaganda purposes, that the M.S.406 was the finest fighter in the world...but it was certainly a pleasant machine to fly with no vices and great maneuverability".

Those that remained in Vichy France's control saw action in Syria against encroaching RAF forces, and on Madagascar against the Fleet Air Arm of the Royal Navy, suffering heavy losses against the service's Fairey Fulmar fighters.

Finland purchased additional M.S.406s (as well as a few 406/410 hybrids) from the Germans, while others were passed off to Italy and some 48 aircraft were delivered to the Air Force of the Independent State of Croatia during 1943.

A number of M.S.406s stationed in Indochina downed several Thai fighters before all French Air Force units were withdrawn from the theatre.

[26] The Finnish nicknames were Murjaani ("moor" or "Negro"), a twist on its name, and Mätimaha (roe-belly) and Riippuvatsa (hanging belly) because of its bulged ventral fuselage.

The M.S.405 was a low-wing monoplane of mixed construction, being furnished with a fabric-covered wooden tail and a bonded metal/wood material (Plymax) skin fixed to duralumin tubing.

The result was the M.S.410, which included the adoption of a stronger wing, simpler fixed radiator in place of the earlier retractable design, an arrangement of four belt-fed MAC guns (which were heated by hot air to prevent the frequent jamming of the wing guns at low temperatures suffered by the M.S.406) in place of the earlier pair of drum-fed weapons, and the fitting of exhaust ejectors for additional thrust.

Two MS.406H fighters were supplied to Switzerland in September 1938 and April 1939 to serve as pattern aircraft as the D-3800,[31][32] retaining the earlier wing design of the 405, but powered by the newer Hispano-Suiza 12Y-31 engines as used by the MS.406.

Pre-production started with a run of eight aircraft from EKW with engines built by Adolph Saurer AG driving a new Escher-Wyss EW-V3 fully adjustable propeller.

The Dornier-Altenrhein factory completed a prototype powered with a licensed-produced HS-51 12Y engine, generating 790.4 kW (1,060 hp) together with the fixed radiator and revised exhausts as tested on the MS.411, in October 1940.

After being retired from operational use as a fighter when the North American P-51 Mustang was acquired in 1948, the type remained in service as a trainer and target tug until 1959.

By this point, the fighters were hopelessly outdated,[23] but the Finns were so desperate for serviceable aircraft that they decided to start a modification program to bring all of their examples to a new standard.

The aircraft designer Aarne Lakomaa turned the obsolete "M-S" into a first rate fighter, the Mörkö-Morane (Mörkö is the Finnish for "Bogeyman" or "Bugbear").

The Germans also supplied captured Klimov M-105P engines (a licensed version of the HS 12Y) of 820.3 kW (1,100 hp) with a fully adjustable VISh-61P propeller to power the Moranes.