Soon after design of the XB-33 began, Martin engineers decided it would be more productive to make a drastic overhaul to the design than to continue developing it and the two prototypes ordered by the USAAF were not built.
Soon after design of the XB-33 began it became clear that a twin-engined aircraft would not achieve the performance requested by the army. The company moved on to developing a larger four-engined design and the two prototypes ordered by the USAAF were not built.