During the early stages of the Second World War, the type was capable of holding its own during the so-called Phoney War. However, upon the invasion of France breaking out in earnest in May 1940, a total of approximately 400 Moranes were lost. Out of these, around 150 were lost to enemy fighters and ground fire, while another 100 aircraft were destroyed on the ground during enemy air raids; the remainder were deliberately destroyed by French military personnel to prevent the fighters from falling into enemy hands intact. In return, French M.S.406 squadrons had achieved 191 confirmed victories, along with another 83 probable victories. Limited production of the type continued in France for sometime after the 1940 Armistice under German supervision.