Quote Originally Posted by HalcyonDays View Post
Not really. The 720 is a derivative of the 707, originally the 707-020, but renumbered 720 for United. The 707 and 720 are, crucially, the wider fuselage airframes (military designations C-137, E-3, E-6....), while the C-135 is a narrower fuselage airframe. The (K)C-135 carries the Boeing model number 717. Different airframe structures derived from the 367-80.
To ad confusion following the Boeing-McDonnell Douglas merger the last of the MD80 line were renamed Boeing 717.