Mil Designator for Boeing 707...........C-135.........KC-135, VC-135, as the 707 got bigger went to VC 137......... First Airforce One was a VC-137. KC-135 with the fan jets were the B model.

KC-135 are still flying in service with beefed up wings and Hi-Bypass engines. Some of these airframes were built in the 1960's.

I was a Crew Chief on NKC-135 J for several years s/n 51-3124 built in 1953.

Those were the days!