Who worked on flight their whole lives without ever building a plane, 50 years after the airplane had been demonstrated? Even in fusion, people are usually buil

Who worked on flight their whole lives without ever building a plane, 50 years after the airplane had been demonstrated? Even in fusion, people are usually building machines. It seems to me the "paper reactor" situation in fission is rather unique. The only precedent I can think of is perhaps the abandonment of shipbuilding in Ming China.