03/31/2012. Remarks by Johan Visschedijk: "Prior to the Franco-German Armistice, the M.S.412, an improved version of the M.S.406, was under development primarily to fulfill a Swiss requirement. As an interim development aircraft, the twelfth pre-series M.S.405 had been fitted with the more powerful Hispano-Suiza 12Y45 engine and flown as the M.S.411, but a prototype of the M.S.412 with the still more powerful Hispano-Suiza 12Y51 engine was not completed in France, the program continuing by Dornier-Werke AG (Doflug) in Switzerland as the D-3801.

Flown for the first time in October 1940, the D-3801 had the 1,050 hp 12Y51 engine, a fixed radiator bath similar to that developed for the M.S.410 and belt-fed 0.295 in (7.5 mm) wing machine guns. Although protracted teething troubles were suffered by the Saurer-built 12Y51 engine, series production of the D-3801 was undertaken by Doflug, Eidgenössisches Flugzeugwerke (EFW) and SWS (Schweizerischen Waggonfabrik Schlieren), deliveries commencing in 1941 and continuing until 1945, and a total of 207 being manufactured.

These were augmented by a further 17 built in 1947-48 from spare assemblies remaining from the main production run. After withdrawal from first-line service, some D-3801s remained in use as advanced trainers and target-tugs until 1959. The pictured J-243 was delivered to the Swiss AF on September 14, 1945, it was lost on October 12, 1953 when it touched the ground with high speed at the Axalp range, pilot Hans Lavater was killed.

One aircraft is restored in 1999 and still in airworthy condition, see page 4731."