The invention relates to a muscle-powered ornithopter comprising a fuselage, a pair of flapping wings which have an alterable profile or a rudder in an outer wing region located at a distance from the fuselage, said alterable profile or rudder allowing the uplift to be modified in a predefined flow, and an elevator unit in which the deflection of the elevator can be modified. The pair of flapping wings and the fuselage are made of an elastic material, the elasticity of which allows the pair of flapping wings to be flapped. The flapping wings are curved downward in a resting position. The elasticity is calculated such that the flapping wings are urged into a neutral position during a flight because of the pilot's weight. The fuselage is designed to accommodate the pilot in an upright position relative to a longitudinal axis of the fuselage such that the pilot can apply stress to and relieve stress from the aircraft in phases by stretching and bending his or her legs. The ornithopter further comprises mechanisms which allow the alterable outer wing regions and the modifiable deflection of the elevator to be actuated in phase with the movement of the flapping wings.