This week in history – April 9, 1957: First flight of KB-50J, jet-augmented tanker Published April 11, 2013 By AFNWC Historian Air Force Nuclear Weapons Center KIRTLAND AFB, N.M. -- In January 1948, former bomber commander and the first Chief of Staff of the Air Force, Gen. Carl A. "Tooey" Spaatz, identified in-flight refueling as the young service's highest initial priority. Two months later, Airmen from Wright-Patterson AFB, Ohio, visited Britain's Flight Refueling Limited, evaluated the company's loop-hose air refueling system design, and bought two examples. The two refueling systems went to Boeing's Wichita, Kan., plant for installation in B-29s. The subsequent conversion program resulted in the production of 40 KB-29M tankers and 40 B-29MR receivers. The Boeing B-50 began as an upgrade to the highly successful B-29. However, the large number of changes - including new engines, modified wings, and a larger tail - resulted in a new designation for the aircraft. The first aircraft entered service in 1947 and eventually 370 were built. As the B-50s began to be replaced by other types of bombers, Tactical Air Command modified them for use as aerial- refueling tankers. The first modifications involved removing all armament and installing extra fuel tanks in the fuselage and under the wings. Eventually, greater speed was needed to keep up with the faster fighters in use, and two J-47 turbojet engines replaced the external tanks. In this form, the aircraft continued to serve well into the 1960s.