The KC-135 Stratotanker's principal mission is air refueling. This unique asset greatly enhances the Air Force's capability to accomplish its primary missions of Global Reach and Global Power. It also provides aerial refueling support to Air Force, Navy and Marine Corps aircraft as well as aircraft of allied nations. The KC-135 is also capable of transporting litter and ambulatory patients using patient support pallets during aeromedical evacuations.
Nearly all internal fuel can be pumped through the flying boom, the KC-135's primary fuel transfer method. A special shuttlecock-shaped drogue, attached to and trailing behind the flying boom, may be used to refuel aircraft fitted with probes. Some aircraft have been configured with the Multipoint Refueling System or MPRS. One crewmember, known as the boom operator, is stationed in the rear of the plane and controls the boom during in-flight air refueling.