An aviation enthusiast since childhood, Dr. Johnson ultimately joined the U.S. Air Force during medical school and earned his wings during his 24 years of military service. After serving as a cancer specialist, flight surgeon and ultimately hospital commander, Dr. Johnson retired as a Colonel in 1999. He holds single and multi engine land plane ratings, as well as single engine seaplane, instrument and commercial pilot certificates. He built his own award-winning Lancair IV-P experimental aircraft, and in 1995 was a finalist in the NASA mission specialist astronaut candidate selection pool.