Turbofan propulsion system for an aircraft, the turbofan propulsive system comprising: - a core engine, extending along an axial direction, and adapted to define, internally, a first flow path for air; - an engine nacelle, arranged at least partially around the core engine, and comprising a front portion of the engine nacelle; - a bypass duct, comprised between the core engine and the engine nacelle and adapted to define a second flow path for air; - a thrust reverser system arranged downstream the front portion of the engine nacelle of the engine nacelle, and the fixed structure of the thrust reverser system being arranged connected to said front portion of the engine nacelle; the thrust reverser system comprising: - a fixed structure and a translating structure adapted to define internally a sequential flow path for air, the translating structure being arranged slidable along the axial direction between a stowed position, wherein the translating structure is sealingly connected to said fixed structure, and an open position, wherein the translating structure is spaced apart from said fixed structure in the axial direction so as to define a circumferential opening between said translating structure and said fixed structure, said opening being adapted to allow the outflow of air towards the external environment; - an iris mechanism, comprising a plurality of blades jointly movable between a rest configuration, wherein they jointly define a passage for air, and a deployed configuration wherein said plurality of blades is adapted to at least partially occlude said passage; - a pylon, adapted to support said turbofan propulsion system by connecting said engine nacelle to a wing of said aircraft; - a pylon coupling system adapted to suspend the thrust reverser system to the pylon and to allow a translation movement along a direction parallel to the axial direction of the translating structure of the thrust reverser system; wherein the iris mechanism is permanently constrained to the pylon coupling system and is adapted to be connected to the translating structure for translation with the latter; and wherein each blade of the iris mechanism has at least one pin and one recess each adapted to cooperate with a recess and pin of adjacent blades, respectively, so that, in the deployed configuration, the relative position of the blades is locked. - a core engine, extending along an axial direction, and adapted to define, internally, a first flow path for air; - an engine nacelle, arranged at least partially around the core engine, and comprising a front portion of the engine nacelle; - a bypass duct, comprised between the core engine and the engine nacelle and adapted to define a second flow path for air; - a thrust reverser system arranged downstream the front portion of the engine nacelle of the engine nacelle, and the fixed structure of the thrust reverser system being arranged connected to said front portion of the engine nacelle; the thrust reverser system comprising: - a fixed structure and a translating structure adapted to define internally a sequential flow path for air, the translating structure being arranged slidable along the axial direction between a stowed position, wherein the translating structure is sealingly connected to said fixed structure, and an open position, wherein the translating structure is spaced apart from said fixed structure in the axial direction so as to define a circumferential opening between said translating structure and said fixed structure, said opening being adapted to allow the outflow of air towards the external environment; - an iris mechanism, comprising a plurality of blades jointly movable between a rest configuration, wherein they jointly define a passage for air, and a deployed configuration wherein said plurality of blades is adapted to at least partially occlude said passage; - a fixed structure and a translating structure adapted to define internally a sequential flow path for air, the translating structure being arranged slidable along the axial direction between a stowed position, wherein the translating structure is sealingly connected to said fixed structure, and an open position, wherein the translating structure is spaced apart from said fixed structure in the axial direction so as to define a circumferential opening between said translating structure and said fixed structure, said opening being adapted to allow the outflow of air towards the external environment; - an iris mechanism, comprising a plurality of blades jointly movable between a rest configuration, wherein they jointly define a passage for air, and a deployed configuration wherein said plurality of blades is adapted to at least partially occlude said passage; - a pylon, adapted to support said turbofan propulsion system by connecting said engine nacelle to a wing of said aircraft; - a pylon coupling system adapted to suspend the thrust reverser system to the pylon and to allow a translation movement along a direction parallel to the axial direction of the translating structure of the thrust reverser system; wherein the iris mechanism is permanently constrained to the pylon coupling system and is adapted to be connected to the translating structure for translation with the latter; and wherein each blade of the iris mechanism has at least one pin and one recess each adapted to cooperate with a recess and pin of adjacent blades, respectively, so that, in the deployed configuration, the relative position of the blades is locked.