After the war Boeing developed the Model 367, a military transport based on the B-29 bomber with a double-lobe fuselage consisting of two intersecting circular sections, so that the 74-foot-long upper deck had a larger diameter. There were 888 C-97s built between 1947 and 1958. Sales of the KC-97s helped pull Boeing out of the post-war slump, and because they extended the range of bombers and fighters, the KC-97 tankers became crucial to SAC operations.