Originally Posted by
tdracer
So Boeing completely changed to fuselage to also allow six abreast seating.
Which directly led to the most obvious external difference between the two aircraft: the 707 has what became the classic Boeing double-bubble; the C-135/KC-135 has what appears to be a circular fuselage cross-section (it isn't, in fact, but there's no visible demarcation between the upper and lower lobe).