An aircraft of a modular type including: at least one rotor suitable for providing in full or in part propulsion and/or lift for the aircraft; at least one power plant of the combustion engine type or of the electric motor type; a main gearbox, for mechanically transmitting drive torque generated by the at least one power plant to the at least one rotor; and an avionics system for assisting in piloting the aircraft. In accordance with the invention, the avionics system is configured for automatically providing the assistance in piloting the aircraft when the aircraft has a first power plant only or when the aircraft has a first power plant and a second power plant.