Thorsness enlisted in the Air Force in 1951 at the age of 19 because his brother was then serving in the Korean War. In 1954, he received his commission as an officer and his wings with a rating of pilot through the USAF Aviation Cadet program in Class 54-G. He later earned a bachelor's degree from the University of Omaha in 1964, and a master's degree in Defense Systems Management from the University of Southern California. His initial assignment was as a pilot in the Strategic Air Command and Tactical Air Command, but he completed training as a fighter pilot and flew both F-84 and F-100 jets before transitioning to the F-105 Thunderchief.