A rotary-wing aircraft or fixed-wing aircraft comprising a propulsion device, said aircraft consisting of one or a plurality of rotors and/or one or a plurality of airscrews, the at least one rotor and/or the one or more airscrews being caused to rotate at a variable or constant speed by at least one shaft (Rp1, Rp2, Rp, RAC, H), the said propulsion device including a distributed electric_motor unit (GEMD) configured to ensure propulsion and/or lifting of the aircraft by causing the shaft to rotate, wherein: - the motor unit (GEMD) consists of distributed electric motor elements (Eel, Ee2,..., Een) connected directly to the rotating shaft (Rpl, Rp2, Rp, RAC, H), with no mechanism for the transmission of movement interposed between the motor elements and the shaft, - the distributed electric motor unit (GEMD) comprising a plurality of stacked electric motor elements (Eel, Ee2,..., Een), each electric motor element being connected directly to the rotating shaft (Rpl, Rp2, Rp, RAC, H) and at least one stator and at least one rotor capable of connection to the rotating shaft in order to transmit to it a mechanical powerr, characterised in that: - the mechanical power transmits to the rotating shaft is in accordance with the following equation: Pr = ∑ i = 1 n K i. P im where: • Pr represents the nominal mechanical power necessary for the propulsion and/or for the lifting of the said aircraft, • Pim represents the maximum mechanical power capable of being delivered by the electric motor element on level i, to the shaft (Rp1, Rp2, Rp, RAC, H),where Pim<Pr, • Ki represents the power derating of the electric motor element on level i, where 0≤ki≤1, Ki being a variable that is adjustable as a function of the valid number of electric motor elements and/or as a function of the nominal mechanical power (Pr) necessary for the propulsion and/or for the lifting of the aircraft at a moment in time t, • n represents the number of electric motor elements comprising the distributed electric motor unit (GEMD), where n≥2, - the axes of rotation of the moving rotors (Rt) and of the shaft (Rp1, Rp2, Rp, RAC, H) being coaxial, - the electric motor elements (Ee1, Ee2,..., Een) are physically separated from each other and each of the electric motor elements is inserted into a dedicated housing. - the motor unit (GEMD) consists of distributed electric motor elements (Eel, Ee2,..., Een) connected directly to the rotating shaft (Rpl, Rp2, Rp, RAC, H), with no mechanism for the transmission of movement interposed between the motor elements and the shaft, - the distributed electric motor unit (GEMD) comprising a plurality of stacked electric motor elements (Eel, Ee2,..., Een), each electric motor element being connected directly to the rotating shaft (Rpl, Rp2, Rp, RAC, H) and at least one stator and at least one rotor capable of connection to the rotating shaft in order to transmit to it a mechanical powerr, - the mechanical power transmits to the rotating shaft is in accordance with the following equation: Pr = ∑ i = 1 n K i. P im where: • Pr represents the nominal mechanical power necessary for the propulsion and/or for the lifting of the said aircraft, • Pim represents the maximum mechanical power capable of being delivered by the electric motor element on level i, to the shaft (Rp1, Rp2, Rp, RAC, H),where Pim<Pr, • Ki represents the power derating of the electric motor element on level i, where 0≤ki≤1, Ki being a variable that is adjustable as a function of the valid number of electric motor elements and/or as a function of the nominal mechanical power (Pr) necessary for the propulsion and/or for the lifting of the aircraft at a moment in time t, • n represents the number of electric motor elements comprising the distributed electric motor unit (GEMD), where n≥2, • Pr represents the nominal mechanical power necessary for the propulsion and/or for the lifting of the said aircraft, • Pim represents the maximum mechanical power capable of being delivered by the electric motor element on level i, to the shaft (Rp1, Rp2, Rp, RAC, H),where Pim<Pr, • Ki represents the power derating of the electric motor element on level i, where 0≤ki≤1, Ki being a variable that is adjustable as a function of the valid number of electric motor elements and/or as a function of the nominal mechanical power (Pr) necessary for the propulsion and/or for the lifting of the aircraft at a moment in time t, • n represents the number of electric motor elements comprising the distributed electric motor unit (GEMD), where n≥2, - the axes of rotation of the moving rotors (Rt) and of the shaft (Rp1, Rp2, Rp, RAC, H) being coaxial, - the electric motor elements (Ee1, Ee2,..., Een) are physically separated from each other and each of the electric motor elements is inserted into a dedicated housing.