Propulsion assembly for an aircraft, said propulsion assembly having a median vertical plane and having: - a turbomachine, - a pylon, - at the front, a front engine attachment fastening the turbomachine to the pylon, - at the rear, a rear engine attachment fastening the turbomachine to the pylon, and - a device for reacting thrust forces (150, 350, 550) having: - a main fitting fastened beneath the pylon, - a spreader mounted so as to be able to pivot on the main fitting about a main axis and having an opening, - two rods (302, 304) for reacting the thrust forces of the engine that are disposed on either side of the median vertical plane, each rod (302, 304) having a front end (302b, 304b) articulated to the turbomachine and a rear end (302a, 304a) articulated to the spreader, wherein each rod (302, 304) has a longitudinal axis (T1, T2), wherein the two longitudinal axes (T1, T2) define a mean plane for transmission of the thrust forces, wherein the main axis is orthogonal to the mean plane for transmission of the thrust forces and comprised in the median vertical plane, wherein the rear end (302a, 304a) of each rod (302, 304) is articulated to the spreader about a front connection axis (L1, L2) parallel to the main axis and wherein the two front connection axes (L1, L2) are symmetrical with respect to the median vertical plane, - a secondary fitting fastened beneath the pylon in front of the main fitting and having a secondary female clevis constituted of two secondary arms (332a-b), each one being passed through by a hole of oblong shape wherein the two holes are aligned along a secondary axis included in the mean plane for transmission of the thrust forces and perpendicular to the median vertical plane, and wherein the major axis of each hole is included in the mean plane for transmission of the thrust forces and perpendicular to the secondary axis, wherein the spreader is housed in the secondary female clevis of the secondary fitting, wherein the opening is coaxial with the secondary axis, and - a backup connection pin inserted with a tight fit into the opening and with clearance into the holes. - a turbomachine, - a pylon, - at the front, a front engine attachment fastening the turbomachine to the pylon, - at the rear, a rear engine attachment fastening the turbomachine to the pylon, and - a device for reacting thrust forces (150, 350, 550) having: - a main fitting fastened beneath the pylon, - a spreader mounted so as to be able to pivot on the main fitting about a main axis and having an opening, - two rods (302, 304) for reacting the thrust forces of the engine that are disposed on either side of the median vertical plane, each rod (302, 304) having a front end (302b, 304b) articulated to the turbomachine and a rear end (302a, 304a) articulated to the spreader, wherein each rod (302, 304) has a longitudinal axis (T1, T2), wherein the two longitudinal axes (T1, T2) define a mean plane for transmission of the thrust forces, wherein the main axis is orthogonal to the mean plane for transmission of the thrust forces and comprised in the median vertical plane, wherein the rear end (302a, 304a) of each rod (302, 304) is articulated to the spreader about a front connection axis (L1, L2) parallel to the main axis and wherein the two front connection axes (L1, L2) are symmetrical with respect to the median vertical plane, - a secondary fitting fastened beneath the pylon in front of the main fitting and having a secondary female clevis constituted of two secondary arms (332a-b), each one being passed through by a hole of oblong shape wherein the two holes are aligned along a secondary axis included in the mean plane for transmission of the thrust forces and perpendicular to the median vertical plane, and wherein the major axis of each hole is included in the mean plane for transmission of the thrust forces and perpendicular to the secondary axis, wherein the spreader is housed in the secondary female clevis of the secondary fitting, wherein the opening is coaxial with the secondary axis, and - a backup connection pin inserted with a tight fit into the opening and with clearance into the holes.