Simulations, which are often used in the training of pilots, military personnel, and health professionals, are turned to when it is too expensive or dangerous to allow students to use the real equipment and when a mistake would be costly. For example, flight simulators are used to train pilots to operate aircraft in extremely hazardous situations without placing a real aircraft, as well as the student and instructor, in danger. This process of interactive learning through critical thinking and problem solving creates a much stronger learning environment than traditional passive instruction.