The original engines of the Potez 630-01 were progressively replaced with improved models of Hispano-Suiza engine, gradually increasing thrust to reach 700 hp on takeoff. At its maximum takeoff weight of 3,850 kg, the prototype was capable of a maximum speed of 460 km/h and a maximum range of 1,300 km when flown at an economical cruising speed of 300 km/h. In March 1937, the second prototype, designated Potez 630-02, performed its maiden flight from Méaulte. The Potez 631-01 was damaged after a landing with its landing gear not being locked into the down position; after repairs, it was handed over to CEMA for official trials in November 1937.