 The only American bombers that could carry the Fat Man were the B-29 and the Convair B-36.In November 1945, the Army Air Forces asked Los Alamos for 200 Fat Man bombs, but there were only two sets of plutonium cores and high-explosive assemblies at the time.The Army Air Forces wanted improvements to the design to make it easier to manufacture, assemble, handle, transport, and stockpile.