By September 1938, the Potez 630 had begun to supplant the obsolete Bloch MB.200 bomber in the fighter direction role; however, the Potez 630's engines proved so troublesome in service that most units were rapidly re-equipped with the Potez 631 prior to the outbreak of the Second World War. By 1 April 1939, a total of 77 Potez 630 and 88 Potez 631 aircraft had been accepted by the French Air Force. The retirement of other obsolete French aircraft, such as the Morane-Saulnier M.S.225 and Dewoitine D.510, could be accommodated for by the increasing numbers of Potez 631s. Just prior to the outbreak of the Second World War, the French Air Force had 85 Potez 630s, 206 Potez 631s, 22 Potez 633s, 63 Potez 633s, and 5 Potez 63.11 aircraft.