AbstractThis chapter makes the distinction between the experience of aviation professionals, often quantified in terms of hours of flight time, or flight qualifications, and expertise, as revealed by high proficiency at aviation tasks. Very high proficiency defines the expert. Challenge results because of the difficulty in measuring such proficiency, particularly beyond the student pilot level, and in air traffic control. The chapter also reviews the literature that examines the relation between experience, differences in cognitive ability, and the expertise of aviation professionals as pertains to controlling the aircraft, navigating, and communicating, as well as pertains to non-technical skills manifest by both pilots and air traffic controllers: situation awareness, decision making, task management and crew resource management. It is concluded that experience is only loosely coupled with proficiency in these areas.