NASA replied that the idea had technological merit, encouraging Northrop that his flying wing concepts had not been completely abandoned. By the late 1970s a variety of illnesses left him unable to walk or speak. Shortly before his death, he was given clearance to see designs and hold a scale model of the Northrop Grumman B-2 Spirit stealth bomber, which shared design features of his YB-35 and YB-49.[13][14] The B-2, for example, has the same 172-foot wingspan as the jet-powered flying wing, YB-49.[14] Northrop reportedly wrote on a sheet of paper "Now I know why God has kept me alive for 25 years".[14] B-2 project designer John Cashen said, "As he held this model in his shaking hands, it was as if you could see his entire history with the flying wing passing through his mind."[15] He died 10 months later.