The Bloch MB-157 was a new fighter designed to take advantage of the powerful Gnome & Rhome 14R radial engine. This engine was much heavier than the earlier engines used in the MB-152 and MB-155 and an attempt to fit it into a MB-152 fuselage failed (MB-156).
Work proceeded quickly on the new aircraft. The new aircraft was wider and longer than the MB-157, with a much cleaner fuselage, although it was obvious related to the earlier aircraft. Work on the prototype began in December 1939. It was to be armed with two 20 mm cannon and four 7.5 mm machine guns, and use the 14R-4 engine. This provided 1,590 hp at take off and 1,700 hp at 26,250 ft, a massive leap from the 1,120 hp of the 14N-25 engine used in the MB-155.
Work on the MB-157 was disrupted by the German invasion. It had been being developed at Villacoublay, near Paris. An attempt to remove it to Poitiers failed, and work continued on the prototype under German control. The prototype finally flew in March 1942 and demonstrated outstanding performance, with a top speed of 441 mph at 25,750 feet. It would have been one of the fastest fighters of the war, with a much higher top speed than any equivalent Bf 109, or indeed all but the fastest Spitfires.
In early 1943 the MB-157 was flown to Paris. Once there the engine was removed for further tests, eventually reaching Germany. The fuselage remained at Orly airport until destroyed in an allied air raid.