The first KB-50 flew in December 1955 and was accepted by the Air Force in January 1956. The tankers steadily entered the operational inventory of TAC supplanting TAC's KB-29s. By the end of 1957, all of the command's aerial refuling squadrons had their full complement of KB-50s. KB-50s, and later KB-50Js with two General Electric J47 jet engines were used by TAC, and also by USAFE and PACAF overseas as aerial tankers. Some were deployed to Thailand and flew refueling missions over Indochina in the early years of the Vietnam War until being retired in March 1965 due to metal fatigue and corrosion.