The invention relates to a convertible aircraft operating method. According to the invention, the aircraft comprises: a fuselage, standard fixed wings which are equipped with ailerons, a tail unit with flight-control surfaces, engines, a rotor with blades, a transmission which is placed between the engines and the rotor and which is equipped with rotor clutch and braking means, a landing gear, means for transition from helicopter mode to autogyro mode and vice versa, and means for direct or reverse transition from autogyro/helicopter mode to aeroplane mode. The lift for a range of low speeds is produced by means of the rotor, while the lift for a range of high speeds is produced by means of the wings. In addition, the lift for a range of intermediate speeds can be produced using the wings and the rotor in autogyro mode simultaneously, and take-off and landing can be performed in autogyro mode or in helicopter mode with the engines coupled to the rotor. The aircraft comprises a hybrid helicopter/autogyro/aeroplane aircraft and, as such, can perform the direct or reverse transition to aeroplane mode from both helicopter mode and autogyro mode.