In 1993, Boeing chose not to pursue development of this concept, focusing instead on updates to the 747.
To Europe With 50 tons", "Popular Science", March 1950, early article with drawing of first layout of XC-99* "Biggest Air Freighter Goes To War" 1951 article on first operational use of XC-99, photos and drawings* National Museum of the USAF, XC-99 photos, along with the photo of the 1/72nd scale XC-99 model by Lt. Col. Howard Meek