A KC-135R Stratotanker assigned to the 6th Air Refueling Wing, 91st Air Refueling Squadron, at MacDill Air Force Base, Fla., flies a training mission over central Florida. The KC-135's principal mission is air refueling. This asset greatly enhances the U. S. Air Force's capability to accomplish its mission of Global Engagement. It also provides aerial refueling support to U.S. Navy, U.S. Marine Corps and allied aircraft. Four turbofans, mounted under 35-degree swept wings, power the KC-135 to takeoffs at gross weights up to 322,500 pounds (146,285 kilograms). Nearly all internal fuel can be pumped through the tanker's flying boom, the KC-135's primary fuel transfer method. A special shuttlecock-shaped drogue, attached to and trailed behind the flying boom, may be used to refuel aircraft fitted with probes. An operator stationed in the rear of the plane controls the boom.