Fly Fighters Jet - MiG-29, MiG-31, L-39

As company specializing in arranging flights in fighter jets to non-pilots, we find ourselves often confronted with interested clients worrying about the risks involved in flying jet. Everybody knows that jet pilots who regularly fly a fighter jet are athletes who spend a significant time of their work in gyms, strengthening both their body and their mind. Why, people ask, can john doe also fly in a fighter jet and even control the aircraft himself without such training and background?