Now the XB-21 was designed to a somewhat vague U.S. Army Air Force requirement that sought an increase in payload and range over the existing Martin B-10. This cutaway addressed that payload capacity, but, instead of showing its bomb capacity, the drawing shows it loaded with supply boxes and twelve airmen. Its normal crew complement was eight, and you have to wonder why even eight were needed on a medium bomber. Only one of these rotund bombers was built as it was slower than the airplane it was designed to replace. However, NAA learned from it and the following private venture NA-40 how to build the much more successful B-25.
