The new Hispano-Suiza 12Ygrs engine driving a two-pitch Chauvière propeller powered the first "M.S405-1" prototype, which flew on 8 August 1935. First flown by French aerobatic pilot Michel Détroyat, the first prototype demonstrated the type's favourable flying characteristics from the onset. Early test flights were flown with a fixed undercarriage, this was replaced by a retractable counterpart later on. After 80 hours of test flights, in January 1936, the prototype was delivered with all military equipment fitted to CEMA at Villacoublay to participate in service trials. On 19 June 1937, the first prototype generated substantial publicity when Détroyat flew it from Paris to Brussels, Belgium, to be displayed at the Brussels Aeronautical Exhibition.