Just to add on, cause i can. Now this is not fact, because i can;t find the numbers to fsupport the premise. But, I've heard for a long time that the KC
-135's had been desingated B-717's by boeing for years. One of the diffenreces in the B-707 and 135/717 was the cabin width. Initially (i beleive, can't really besure i'm gettting this right, so you experts fel free to chime in and correct) 367-80 would only support an 2/3 width for seats. Boeing changed this to meet the 3/3 width becasue of the DC-8, story goes event hough Boeing had the flying proto-type, DOuglas was promising the airlines more since they had a "paper" airplane and an eraser here and there would fix that. SO, airlines wanted 6-abreats seating, BOeing said, fine, on the production model we'll make the cabin wider (and designate it B-707). Appearently the military really didn't care so much if you had 3/3 seating capacity so they were fine with a model based on the 367-80 width, and was designated the B-717. The fact that boeing internally at least designated the KC
-135 as the B717 is actually on their web page if you look under the commercial airplan group at the 707 page.
The 707 fuselage became the standard used for Boeing narrowbodies until now. The 727,737, 757 all have the same fuselage width. So here comes this little project for Valujet called the MD
-95, based on the narrower (than a borring narrowbody) fuselage of the DC-9 serries airplanes. BOeing buys MD
before it can deliver and really produce any planes (and around the same time Valujet morphs into AIrtran). So, this MD
-95 has a similar fuselage cross section of the KC
-135/B717... lets just rename it that!! (I wonder if it was that simple or is someone spent months arguing over it)
Again, standard disclaimer, i could be wrong. BUt at anyrate, realy odd ball jet number from Boeing i always wondered about.. the B-720... where did they get that?