Air traffic controllers are people trained to maintain the safe, orderly and expeditious flow of air traffic in the global air traffic control system. The position of air traffic controller is one that requires highly specialized knowledge, skills, and abilities. Controllers apply separation rules to keep aircraft at a safe distance from each other in their area of responsibility and move all aircraft safely and efficiently through their assigned sector of airspace, as well as on the ground. Because controllers have an incredibly large responsibility while on duty (often in aviation, "on position") and make countless real-time decisions on a daily basis, the ATC profession is consistently regarded around the world as one of the most mentally challenging careers, and can be notoriously stressful depending on many variables (equipment, configurations, weather, traffic volume, human factors, etc.). Many controllers, however, would cite high salaries, and a very large, unique, and privileged degree of autonomy as major advantages of their jobs.