I had thought of Howard Hughes as well. And wasn't Phil Condit, who rose from a design engineer to be Chairman of Boeing also a test pilot ? He was certainly a PPL as soon as he could be, even before he went to university, and is an all-round aviation buff as well. Do I recall he has his own Pitts or similar ? Led much 747 design work, and, just on the side, he ran the 727 sales during the years that it became dominant. If you're reading this Phil, in your well-earned retirement, Hi ! Bet the 787 wouldn't have been 3 years late if you were still there.