Abstract: An assembly for an aircraft comprising a pylon having a mounting plate having a front face and a rear face and through which there passes, between the front face and the rear face, at least one central bore, a front engine mount comprising a spar with a rear face bearing against the mounting plate front face and which, for each central bore, has a complementary central bore aligned with the central bore, and for each central bore, a mounting system. The mounting system comprises a shear pin inserted into the central bore and the complementary central bore from the rear face with a flange bearing against the rear face, a support with a central hole, the diameter of which is greater than the flange diameter and fixed to the rear face, and a cap fixed to the support closing off the central hole and bearing against the shear pin.