 He was less than impressed with this expensive and under-performing aircraft, preferring the Boeing B-50 Superfortress, an upgraded version of the B-29 instead.The USAF, however, had staked much of its credibility on the B-36, something that Kenney did not seem to appreciate.In the context of the Berlin Blockade in June 1948, the Air Force Chief of Staff, General Hoyt S. Vandenberg met with Forrestal to report the poor state of SAC.