Morane-Saulnier was a prolific designer and builder of aircraft since its founding in 1911. Beyond World War 1 (1914-1918), the company contributed throughout the Interwar years and into World War 2 (1939-1945) where its aircraft evolved into very modern, very capable combat platforms. The MS.406 series - born from the "MS.405" - was one of the concern's final offerings before the Fall of France in May-June 1940 and this single-seat, single-engine monoplane fighter went on to see service with several forces of the period beyond the French Air Force itself.
Back in September of 1938, the first of two "MS.406H" fighters were given to Switzerland for evaluation and to serve as the basic form for a locally-produced, licensed version of the same French aircraft - this to become the "D-3800" in Swiss service. These aircraft were essentially MS.405 airframes and wings carrying the engine (a Hispano-Suiza 12Y31 inline) of the MS.406 production type though with localized changes to suit a standing Swiss Air Force fighter requirement. For example, the original the drum-fed wing machine guns were converted to belt-fed models already in Swiss service and the two-pitch propeller gave way to a controllable-pitch form of local origination. The aircraft production program was headed by Eidgenossisches Konstruktions-Werkstatte (EKW) with the engines coming from Adolph Saurer AG.
The Swiss Air Force contracted for eight pre-production models constructed to the revised Swiss fighting standard and these were built during 1939. Deliveries then followed in January of 1940 and, into late August 1940, some seventy-four production-quality aircraft were built in all. In 1942, with the war already a daily part of European existence, at least two more fighters were built from what were essentially available spares and this was used to further strengthen Swiss Air Force numbers. The following year, the fleet was modernized with the changes enacted to the "D-3801" standard (detailed elsewhere on this site) - this included an ejector-exhaust system to provide additional forward thrust, upgrading the internal control system, and improved engine cooling.
All told, the streamlined fighter could reach a speed of 295 miles-per-hour and had an endurance of 1.75 hours in the air. Rate-of-climb reached 2,685 feet-per-minute, making them suitable interceptors if needed. Empty weight was 4,000lb against a Maximum Take-Off Weight (MTOW) of 5,500lb. Dimensions included a running length of 26.9 feet, a wingspan of 34.9 feet, and a height of 8.10 feet.
With Switzerland's independent stance during the Second World War, the D-3800 fighter was never exposed to actual combat - despite the very real threat of a German invasion. The fleet served out its days as advanced trainers for future generations of Swiss air men and the final forms were given up for good in 1954 as the jet age began to take hold.