The experimental North American X-15 program at Edwards Air Force Base involves test pilots: civilian Matt Powell (David McLean (actor)), Lt. Col. Lee Brandon (Charles Bronson) and Maj. Ernest Wilde (Ralph Taeger). The cutting edge high-speed program is ramrodded by project chief Tom Deparma (James Gregory (actor)) and US Air Force Col. Craig Brewster (Kenneth Tobey). As the test pilots prepare for the planned launch of the rocket-powered aircraft from a Boeing B-52 Stratofortress Mother ship (aviation), they experience emotional and physical problems, which they share with their wives and sweethearts.