Once active combat had begun, the Potez 631 had quickly proved to be an ineffectual interceptor; it was slower than some German bomber aircraft and 130 km/h slower than the Messerschmitt Bf 109E fighter. Perhaps the most successful unit operating the Potez 631 was the Flottille F1C of the French Naval Air Arm; between 10–21 May 1940, aircraft of the unit shot down 12 enemy aircraft in exchange for 8 of their own losses prior to its withdrawal from active combat.