I believe the 720 had the same cross-section as all other Boeing commercial narrowbodies, but was shorter, with more wing and the big engines. In a message dated 1/23/2006 8:18:09 PM Central Standard Time, RWM@xxxxxxxxxx writes: My recollection is that the "720" was a civil derivative of the C-135, a descendant of the prototype "Dash 80". The 720 had a smaller cabin cross-section than the "707" series, a shorter fuselage, a longer wingspan (than the -100/-120) and operated at lower MTOWs. The 707 series -100/-120 and -300/-320 (and RR powered -400) had a slight double bubble to the cabin cross-section, making it appear to be a wider cabin above the floor. American operated the 720B, 707-123, 707-323B and 707-323C models, the latter operating in both passenger and freighter configurations. Braniff also operated the 720, into South America for its hot and high (La Paz) performance.