The Boeing KC-135 “Stratotanker” was a tanker plane used for aerial refueling. This technique used a ‘flying boom’ system, in which a rigid pipe called the ‘boom’ was extended in order to pump fuel from one plane to the other. The KC-135 Stratotanker was the first jet tanker when it was released in 1954. The Air Force ordered these tankers from Boeing to refuel F-105s, F-4s and B-52s throughout the Cold War and conflicts in Southeast Asia. Though KC-135s are still in use today, the Boeing KC-46 Pegasus is now the preferred tanker for the US military.