Following the withdrawal of the 24 TB-50H trainers from service, they were modified as aerial tankers. Because of structural and equipment differences from the earlier B-50D, they were known as KB-50K, but were otherwise identical to the KB-50Js. A J47 jet engine was installed underneath each wing to boost speed while refuelling and to increase altitute capability. Three probe-and-drogue refuelling stations were installed, one in the tail and one in a pod underneath each outer wing.
All modifications were carried out by the Hayes Aircraft Corporations. The first KB-50K modification was produced in December of 1957 and was accepted by the Air Force in January 1958. Like the KB-50J, the KB-50Ks were assigned to the Tactical Air Command as fighter tanker aircraft. They were all phased out in the early 1960s.