Aircraft and the three-dimensional environment in which they operate are not user-friendly for human beings. As a result, developing and maintaining the proficiencies necessary to safely and efficiently fly an airplane or helicopter are difficult, time-consuming, and costly. Flight training has barely progressed beyond the basics, perhaps because of a typical pilot's limited time and money. Training remains a sort of crash course in not crashing, with almost exclusive concentration on physically coordinating, maneuvering, and manually handling-not manhandling-an aircraft.