Question: Which aircraft originally developed for USAF has been used for medical evacuation as well as SAC joint missions? 
Sentence (from "Boeing C-17 Globemaster III"): It was designed to replace the Lockheed C-141 Starlifter, and also fulfill some of the duties of the Lockheed C-5 Galaxy, freeing the C-5 fleet for outsize cargo.
Relevant evidence: No