A flight surgeon is a military meical officer assigned to duties in the clinical field known as flight, or aviation medicine. (Although the term "flight surgery" is considered improper by purists, it may occasionally be encountered.) Flight surgeons are medical or osteopathic doctors who are primarily responsible for the medical evaluation, certification and treatment of aviation personnel — e.g., pilots, aircrew members and air traffic controllers. They perform routine, periodic medical examinations ("flight physicals") of these personnel. In the U.S military, flight surgeons are trained to fill general public health and occupational and preventative medicine roles, and are only infrequently "surgeons" in an operating theater sense. Flight surgeons may also be called upon to provide medical consultation as members of an investigation board into an aviation mishap.