Assembly (100, 100a-b) for mounting a propulsion system having a vertical median plane on an aircraft, said assembly (100, 100a-b) comprising: - a wing with a front spar, a suction-side panel and a pressure-side panel, which are fastened at the upper portion of the front spar and at the lower portion of the front spar, respectively, wherein a fourth bore and a fifth bore pass vertically through the suction-side panel, - an engine pylon comprising a primary structure, a blade, which is secured to the primary structure and extends to the rear and in the upper portion of the primary structure, and two starboard-side and port-side fastening lugs, which are secured to the primary structure and extend to the rear and along the sides of the primary structure, wherein a first bore, a second bore and a third bore pass vertically through the blade, wherein a sixth bore (272a-b) passes horizontally through each fastening lug (270a-b), and - a starboard-side fitting and a port-side fitting, which have, respectively, a starboard-side female clevis in which the starboard-side fastening lug is inserted and a port-side female clevis in which the port-side fastening lug is inserted, wherein a seventh bore (278a-b) passes through each female clevis (276a-b), the axis of said seventh bore being coaxial with the axis of the sixth bore (272a-b) in the fastening lug (270a-b) inserted therein, and wherein a pin is inserted into the associated bores aligned in this way, said assembly (100, 100a-b) being characterized in that the starboard-side fitting and a port-side fitting are fastened beneath the pressure-side panel and in that the assembly (100, 100a-b) comprises also: - two first shackles arranged vertically on either side of the blade and of the suction-side panel, wherein a first bore of each first shackle is aligned so as to be coaxial with the first bore of the blade, with a pin being inserted into the bores aligned in this way, wherein a second bore of each first shackle is aligned so as to be coaxial with the fourth bore of the suction-side panel, with a pin being inserted into the bores aligned in this way, and - two second shackles arranged vertically on either side of the blade and of the suction-side panel, wherein a first bore of each second shackle is aligned so as to be coaxial with the second bore of the blade, with a pin being inserted into the bores aligned in this way, wherein a second bore of each second shackle is aligned so as to be coaxial with the third bore of the blade, with a pin being inserted into the bores aligned in this way, wherein a third bore of each second shackle is aligned so as to be coaxial with the fifth bore of the suction-side panel, with a pin being inserted into the bores aligned in this way. - a wing with a front spar, a suction-side panel and a pressure-side panel, which are fastened at the upper portion of the front spar and at the lower portion of the front spar, respectively, wherein a fourth bore and a fifth bore pass vertically through the suction-side panel, - an engine pylon comprising a primary structure, a blade, which is secured to the primary structure and extends to the rear and in the upper portion of the primary structure, and two starboard-side and port-side fastening lugs, which are secured to the primary structure and extend to the rear and along the sides of the primary structure, wherein a first bore, a second bore and a third bore pass vertically through the blade, wherein a sixth bore (272a-b) passes horizontally through each fastening lug (270a-b), and - a starboard-side fitting and a port-side fitting, which have, respectively, a starboard-side female clevis in which the starboard-side fastening lug is inserted and a port-side female clevis in which the port-side fastening lug is inserted, wherein a seventh bore (278a-b) passes through each female clevis (276a-b), the axis of said seventh bore being coaxial with the axis of the sixth bore (272a-b) in the fastening lug (270a-b) inserted therein, and wherein a pin is inserted into the associated bores aligned in this way, - two first shackles arranged vertically on either side of the blade and of the suction-side panel, wherein a first bore of each first shackle is aligned so as to be coaxial with the first bore of the blade, with a pin being inserted into the bores aligned in this way, wherein a second bore of each first shackle is aligned so as to be coaxial with the fourth bore of the suction-side panel, with a pin being inserted into the bores aligned in this way, and - two second shackles arranged vertically on either side of the blade and of the suction-side panel, wherein a first bore of each second shackle is aligned so as to be coaxial with the second bore of the blade, with a pin being inserted into the bores aligned in this way, wherein a second bore of each second shackle is aligned so as to be coaxial with the third bore of the blade, with a pin being inserted into the bores aligned in this way, wherein a third bore of each second shackle is aligned so as to be coaxial with the fifth bore of the suction-side panel, with a pin being inserted into the bores aligned in this way.