XV277 Said ;
"the airframe is very different from E-3"
erm....Oh no it isnt.
erm....Yes it is.
The E-3 is based on a 707, the RC-135 is based on the C-135. The C-135 was developed in tandem with the 707, both being based on the "Dash 80" (Boeing 367-80), but with differing lineage. The main visible differences being the airframe dimensions and flight deck.