This is the first B-36, first flown on 8 August 1946. The beast had unprecedented wheel pressure and the XB-36 is seen here fitted with tracked landing gear units which should allow the Peacemaker to bomb Russia from forward polar airfields. The XB-36 did make one flight with this gear before the idea was abandoned. Later the aircraft was used for research into a nuclear-powered B-36 variant. Photo from: US Air Force