The KC-135 Stratotanker and the KC-10 Extender are the aircraft that allow the USAF to make the claim, "any where, any time." They are the legs of all the major commands that allow the USAF to project on a global scale. On average there is a refueling be conducted every five minutes around the clock; around the world. Other nations also have tankers, but to the size of the USAF tanker fleet.