Assembly for an aircraft, said assembly having a pylon and a generally cylindrical nacelle intended to surround an engine of the aircraft, wherein the nacelle has a median plane and comprises: - a structure that is attached to the pylon at a junction between the pylon and said structure, - an air-intake cowl that surrounds an air intake of the nacelle, - lateral cowls disposed on either side of the median plane of the nacelle, - an upper cowl providing the fairing around said junction, - a visor composed of an arcuate cowl that aerodynamically links the air-intake cowl, the lateral cowls and the upper cowl, and - attachment means comprising two centring systems and two tensioning systems, wherein the two tensioning systems are disposed on either side of the median plane of the nacelle and between the two centring systems, wherein each tensioning system comprises: - a first fitting, which is attached to the structure, - a second fitting, which is attached to the visor, - a threaded rod, a first end of which is mounted articulated on the second fitting, - a spring element, and - an arresting means, wherein the first fitting has an engagement wall through which an orifice passes and which has a face that is oriented towards the second fitting and an opposite face, wherein the threaded rod passes through the orifice, wherein the spring element is fitted on the threaded rod and positioned by the face of the engagement wall that is opposite from the second fitting and wherein the arresting means prevents movement of the spring element, wherein each centring system comprises: - a first fitting, which is attached to the structure, and - a second fitting, which is attached to the visor, wherein one of the fittings has a bore, and the other fitting bears a shaft that is accommodated in the bore. wherein the nacelle has a median plane and comprises: - a structure that is attached to the pylon at a junction between the pylon and said structure, - an air-intake cowl that surrounds an air intake of the nacelle, - lateral cowls disposed on either side of the median plane of the nacelle, - an upper cowl providing the fairing around said junction, - a visor composed of an arcuate cowl that aerodynamically links the air-intake cowl, the lateral cowls and the upper cowl, and - attachment means comprising two centring systems and two tensioning systems, wherein the two tensioning systems are disposed on either side of the median plane of the nacelle and between the two centring systems, - a structure that is attached to the pylon at a junction between the pylon and said structure, - an air-intake cowl that surrounds an air intake of the nacelle, - lateral cowls disposed on either side of the median plane of the nacelle, - an upper cowl providing the fairing around said junction, - a visor composed of an arcuate cowl that aerodynamically links the air-intake cowl, the lateral cowls and the upper cowl, and - attachment means comprising two centring systems and two tensioning systems, wherein the two tensioning systems are disposed on either side of the median plane of the nacelle and between the two centring systems, wherein each tensioning system comprises: - a first fitting, which is attached to the structure, - a second fitting, which is attached to the visor, - a threaded rod, a first end of which is mounted articulated on the second fitting, - a spring element, and - an arresting means, - a first fitting, which is attached to the structure, - a second fitting, which is attached to the visor, - a threaded rod, a first end of which is mounted articulated on the second fitting, - a spring element, and - an arresting means, wherein the first fitting has an engagement wall through which an orifice passes and which has a face that is oriented towards the second fitting and an opposite face, wherein the threaded rod passes through the orifice, wherein the spring element is fitted on the threaded rod and positioned by the face of the engagement wall that is opposite from the second fitting and wherein the arresting means prevents movement of the spring element, wherein each centring system comprises: - a first fitting, which is attached to the structure, and - a second fitting, which is attached to the visor, - a first fitting, which is attached to the structure, and - a second fitting, which is attached to the visor, wherein one of the fittings has a bore, and the other fitting bears a shaft that is accommodated in the bore.