Wing for an aircraft, said wing comprising an aerofoil extension (100, 200, 300, 400, 500), said aerofoil extension (100, 200, 300, 400, 500) comprising a suction-side wall and a pressure-side wall, the suction-side wall and the pressure-side wall defining between them a profile of the aerofoil extension, characterized in that the aerofoil extension (100, 200, 300, 400, 500) comprises: - a structural element arranged along the leading edge of the aerofoil extension, - the suction-side wall and the pressure-side wall (206, 204) are joined by a structure (302, 502) that is deformable under the action of aerodynamic pressures acting on the suction-side wall and the pressure-side wall when the aircraft is in flight, and in that: - the suction-side wall comprises a first part which extends downstream from the leading edge of the aerofoil extension, generally as far as the front third of the suction-side wall, the pressure-side wall comprises a rigid part which extends upstream from the trailing edge of the aerofoil extension, generally as far as the front third of the pressure-side wall, the first part of the suction-side wall and the rigid part of the pressure-side wall being respectively made of a rigid material, the suction-side wall further comprises a second part, designated as a semirigid part, between the first part and the trailing edge of the aerofoil extension, having a stiffness below that of the first part of the suction-side wall, and the pressure-side wall further comprises an extendable part which extends upstream from the rigid part; or - the pressure-side wall comprises a first part which extends downstream from the leading edge generally as far as the front third of the pressure-side wall, the suction-side wall comprises a rigid part which extends upstream from the trailing edge, generally as far as the front third of the pressure-side wall, the first part of the pressure-side wall and the rigid part being respectively made of a rigid material, the suction-side wall further comprises a second part, designated as a semirigid part, between the first part and the trailing edge of the aerofoil extension, having a stiffness below that of the first part of the pressure-side wall, and the suction-side wall further comprises an extendable part that extends upstream from the rigid part. - a structural element arranged along the leading edge of the aerofoil extension, - the suction-side wall and the pressure-side wall (206, 204) are joined by a structure (302, 502) that is deformable under the action of aerodynamic pressures acting on the suction-side wall and the pressure-side wall when the aircraft is in flight, - the suction-side wall comprises a first part which extends downstream from the leading edge of the aerofoil extension, generally as far as the front third of the suction-side wall, the pressure-side wall comprises a rigid part which extends upstream from the trailing edge of the aerofoil extension, generally as far as the front third of the pressure-side wall, the first part of the suction-side wall and the rigid part of the pressure-side wall being respectively made of a rigid material, the suction-side wall further comprises a second part, designated as a semirigid part, between the first part and the trailing edge of the aerofoil extension, having a stiffness below that of the first part of the suction-side wall, and the pressure-side wall further comprises an extendable part which extends upstream from the rigid part; or - the pressure-side wall comprises a first part which extends downstream from the leading edge generally as far as the front third of the pressure-side wall, the suction-side wall comprises a rigid part which extends upstream from the trailing edge, generally as far as the front third of the pressure-side wall, the first part of the pressure-side wall and the rigid part being respectively made of a rigid material, the suction-side wall further comprises a second part, designated as a semirigid part, between the first part and the trailing edge of the aerofoil extension, having a stiffness below that of the first part of the pressure-side wall, and the suction-side wall further comprises an extendable part that extends upstream from the rigid part.