Aircraft of modular type including: - at least one rotor capable of providing propulsion and/or lift for said aircraft fully or in part, - at least one power plant (3, 13) of the combustion motor type or of the electric motor type, - a main gearbox for mechanically transmitting a drive torque generated by said at least one power plant (3, 13) to said at least one rotor, and - an avionics system for assisting with the piloting of said aircraft, characterized in that said aircraft includes: - at least two electrical connection interfaces (6, 7) which are continuously electrically connected to said avionics system, a first electrical connection interface electrically connecting the avionics system to a first power plant of said at least one power plant (3, 13) and a second electrical connection interface capable of being left free or electrically connecting the avionics system to a second power plant of said at least one power plant (3, 13), and - at least two mechanical connection interfaces (8, 9) continuously mechanically connected to said main gearbox, a first mechanical connection interface mechanically connecting said main gearbox to said first power plant and a second mechanical connection interface capable of being left free or mechanically connecting said main gearbox to said second power plant, and in that said avionics system is configured for automatically providing said assistance with piloting said aircraft, firstly when only said first power plant is electrically connected to said first electrical connection interface, and secondly when both said first power plant is electrically connected to said first electrical connection interface and said second power plant is electrically connected to said second electrical connection interface. - at least one rotor capable of providing propulsion and/or lift for said aircraft fully or in part, - at least one power plant (3, 13) of the combustion motor type or of the electric motor type, - a main gearbox for mechanically transmitting a drive torque generated by said at least one power plant (3, 13) to said at least one rotor, and - an avionics system for assisting with the piloting of said aircraft, - at least two electrical connection interfaces (6, 7) which are continuously electrically connected to said avionics system, a first electrical connection interface electrically connecting the avionics system to a first power plant of said at least one power plant (3, 13) and a second electrical connection interface capable of being left free or electrically connecting the avionics system to a second power plant of said at least one power plant (3, 13), and - at least two mechanical connection interfaces (8, 9) continuously mechanically connected to said main gearbox, a first mechanical connection interface mechanically connecting said main gearbox to said first power plant and a second mechanical connection interface capable of being left free or mechanically connecting said main gearbox to said second power plant, and in that said avionics system is configured for automatically providing said assistance with piloting said aircraft, firstly when only said first power plant is electrically connected to said first electrical connection interface, and secondly when both said first power plant is electrically connected to said first electrical connection interface and said second power plant is electrically connected to said second electrical connection interface.