United States Air Force Boeing KC-135T Stratotanker 58-0103
On most KC-135 tankers, the fuel system can either offload fuel to another airplane, or feed the airplane's own engines. When the SR-71 high-altitude reconnaissance aircraft entered service, however, it burned a different fuel from regular jets, and so required KC-135 tankers with separate fuel storage. Tankers modified to fuel the SR-71 were designated KC-135Q. When the SR-71 was retired, these tankers underwent the same CFM-56 re-engine modification as the rest of the KC-135 fleet, and were redesignated KC-135T. I believe they are now no different operationally from the standard KC-135R.
United States Air Force Boeing KC-135T Stratotanker 58-0103
On most KC-135 tankers, the fuel system can either offload fuel to another airplane, or feed the airplane's own engines. When the SR-71 high-altitude reconnaissance aircraft entered service, however, it burned a different fuel from regular jets, and so required KC-135 tankers with separate fuel storage. Tankers modified to fuel the SR-71 were designated KC-135Q. When the SR-71 was retired, these tankers underwent the same CFM-56 re-engine modification as the rest of the KC-135 fleet, and were redesignated KC-135T. I believe they are now no different operationally from the standard KC-135R.