A helicopter is an aircraft that can take off and land vertically. Also called a "rotary aircraft," it can hover and rotate in the air and can move sideways and backwards while aloft. It can change direction very quickly and can stop moving completely and begin hovering. A helicopter flies by means of the thrust that is created by the rotation of the blades of a main rotor that is mounted on a shaft above the fuselage, or body, of the aircraft. As the blades rotate, an airflow is created over them, resulting in lift. This raises the helicopter. A pilot maneuvers the helicopter by changing the pitch, or angle, of the rotor blades as they move through the air. An engine is used to create the force needed to lift the aircraft and its passengers and cargo. Reciprocating gasoline and gas turbine engines are the most common types used on helicopters.