If Morane-Saulnier didn’t invent the high-wing monoplane it might have well have, as its "Parasol" monoplane, soon became a popular choice for carrying passengers on sight seeing rides. When World War I started, the Type L received substantial orders as a reconnaissance aircraft, before being assigned to combat duties in 1915, because of its speed and agility. French, British and Russian aviators scored their first victories in it.
Among them Roland Garros achieved the first-ever shooting-down of an aircraft by a machine-gun firing through the propeller, April 1, 1915. He used Saulnier's work on metal deflector wedges attached to propeller blades. MS also designed the first single-seat tractor fighter aircraft, the medium wing Type N, which was nicknamed “Bullet” as it was then the fastest Allied aircraft.
The swept-wing Type AI, introduced in early 1918, saw limited front-line service, though pilots praised its handling qualities. The US Army Air Service purchased 50 of them for advanced training. Some survive today in museums and collections, including examples at Fantasy of Flight and Old Rhinebeck Aerodrome.
After the war with military orders being cancelled, Morane-Saulnier specialized in training aircraft, first for their own flight school near Paris, which helped to sell some aircraft to private owners. Handling qualities of the Morane-Saulnier Parasol trainers, especially with the introduction of auto-stable airfoil on 1929 MS models, resulted in the sale of 3,000 trainers in 37 countries, including the United States. Pilots flying Morane-Saulniers at airshows helped also: in 1928 Alfred Fronval performed 1,111 consecutive loops in 4 hours 56 minutes with his MS 129.
In the mid 30s, the reactivity of the small-sized company and expertise in light airframe helped MS to win France’s fighter aircraft program to replace obsolete fleets with the MS 405, a revolutionary new aircraft project, a contemporary of the Curtiss P-36.
Designed around the Hispano-Suiza V12 liquid-cooled engine, the MS 405 had a host of new features: a full-metal airframe, a retractable landing gear, a variable-pitch propeller, a closed canopy, oxygen and radio. It was the first aircraft ever to be equipped with a sliding canopy. An MS patent was later adopted by many other manufacturers.
The MS 405 prototype made its maiden flight in August 1935, reaching a speed of 280 mph. Unfortunately the program was slowed by political environment. In 1938 large-scale production began for 1,000 MS 406 just in time for World War II but not in enough time to help stop the Nazi invasion.
In 1941, Morane-Saulnier factory near Paris was forced to build the Fieseler Storch, while the design team and some skilled workers moved secretly to a new factory in Tarbes, then in the free zone, to continue works on fighter prototypes, including the fighter-trainer MS 470, which flew for the first time early 1945.