The Morane‑Saulnier M.S.406 was the principal French fighter at the outbreak of the Second World War, entering production in 1938 and becoming one of only two indigenous French aircraft to surpass 1,000 units built.
At the start of the conflict, it was, alongside the Potez 630, one of the few French-designed aircraft capable of exceeding 400 km/h.
Developed in response to a 1934 French Air Force requirement for a modern single‑seat interceptor, Morane‑Saulnier produced the MS.405 prototype—a major technological step for the company.
It was their first low‑wing monoplane, their first design with an enclosed cockpit, and their first aircraft fitted with retractable landing gear.
Entering service in early 1939, the refined M.S.406 became the French Air Force’s first truly modern fighter.
Although agile and sturdy, it was underpowered and lightly armed compared to contemporary designs, and it struggled against the Messerschmitt Bf 109E during the Battle of France.
During the Phoney War (September 1939–May 1940), the type performed adequately, but the German invasion exposed its limitations.
Roughly 400 aircraft were lost: about 150 in combat, around 100 destroyed on the ground, and the remainder deliberately burned by French personnel to prevent capture.
Despite these losses, M.S.406 units claimed 191 confirmed and 83 probable victories.
Limited production continued under German supervision after the June 1940 Armistice.
The M.S.406 saw export interest across Europe.
Poland ordered 160 examples, though none arrived before the outbreak of war.
Finland and Switzerland became its most significant foreign operators, each developing improved indigenous variants such as the Finnish Mörkö‑Morane.
By the end of the war, rapid advances in fighter design had rendered the type obsolete, and its final role was as an advanced trainer in Finland until its retirement in 1952.
Design and Development
Origins In 1934 the French Air Force’s Service Technique de l’Aéronautique issued the “C1” requirement for a modern interceptor to replace the Dewoitine D.371, D.500, and Loire 46. Morane‑Saulnier responded with the MS.405, designed under Paul‑René Gauthier.
The aircraft featured a low‑wing monoplane layout, enclosed cockpit, variable‑pitch propeller, and retractable landing gear—radical departures from the company’s earlier parasol‑wing designs.
Its mixed construction used a metal‑and‑plywood composite skin (Plymax) over a duralumin frame, with a fabric‑covered wooden tail.
Into Flight Powered by an 860 hp Hispano‑Suiza 12Ygrs engine, the first MS.405‑1 flew on 8 August 1935 with test pilot Michel Détroyat.
Early trials confirmed excellent handling.
After military equipment was installed, the prototype underwent service testing in 1936 and gained public attention with a high‑profile flight to the Brussels Aeronautical Exhibition in 1937.
Development continued slowly.
A second prototype, fitted with a 900 hp 12Ycrs engine, first flew in January 1937 and reached 443 km/h in trials.
Both prototypes appeared at the 1937 Paris Air Show.
Sixteen pre‑production aircraft were ordered, incorporating aerodynamic and structural refinements.
These aircraft served as manufacturing pattern examples and as the basis for export derivatives, including the Swiss D‑3800 and D‑3801.
Transition to the M.S.406
The production‑standard M.S.406 introduced a lighter wing structure and a retractable radiator.
Powered by the 860 hp Hispano‑Suiza 12Y‑31, it was slightly faster than the MS.405 and capable of reaching 489 km/h in level flight and over 730 km/h in a dive.
Armament comprised a 20 mm Hispano‑Suiza cannon firing through the propeller hub and two wing‑mounted 7.5 mm MAC 1934 machine guns.
At high altitude the MAC guns were prone to freezing, prompting the addition of heating systems.
Further Development Combat experience in late 1939 led to the improved M.S.410, featuring four heated MAC 1934 guns, a revised windscreen for a new reflector sight, electropneumatic armament controls, and provisions for under‑wing drop tanks.
France ordered 500 conversions in February 1940, but the programme halted in May as all available aircraft were rushed into combat.
Only five complete M.S.410s and 150 upgraded wing sets were finished.
Production
Anticipating war with Germany, France ordered 1,000 M.S.406s in March 1938.
Morane‑Saulnier could not meet this demand alone, so a second production line was established at the nationalised SNCAO factory in Saint‑Nazaire.
Additional orders followed in 1937 and 1938 as part of the French Air Force’s Plan V expansion.
The first production aircraft flew on 29 January 1939.
Output was initially slow due to chronic engine shortages, but by April 1939 production reached six aircraft per day, rising to eleven per day by the outbreak of war. By September 1939, 535 examples were in squadron service.
Production peaked at 147 aircraft in August 1939 before declining as resources shifted to other projects.
By March 1940, the full order of 1,000 fighters had been delivered, along with 77 export aircraft for Finland and Turkey.
Orders for Lithuania and Poland were cancelled after hostilities began.
Foreign interest had been strong.
Belgium considered licensed production through Avions Fairey, though negotiations failed.
Switzerland became the first major export customer, securing a production licence in September 1938 for domestic manufacture at Emmen.
