The B-50 entered service in 1947 with some 370 being built. As they were replaced by more modern equipment, many were converted for use as tankers by Tactical Air Command by the removal of armament and fitment of extra tankage in the fuselage and under the wings. To keep up with the increasing demands from the jets they were serving, the external tanks were replaced by two J47 turbojets. As such, they soldiered on well into the 1960s until fully replaced by KC-97s and moreover KC-135s