An airship, comprising: - a flexible envelope without a rigid internal structure imposing a shape on the envelope, said envelope delimiting an inside space intended to be at least partially filled with a lighter-than-air first gas, extending along a longitudinal axis between a nose located at the front of the airship and a tail located at the back of the airship, and comprising an upper portion located at the top and a lower portion located at the bottom, said lower portion being opposite the upper portion, - a wall located inside the envelope, said wall being flexible, being gas-tight, extending longitudinally between the nose and the tail thus separating the inside space of the envelope into a first space intended to be filled with said first gas and a second space intended to be filled with a second gas, said second space being located on the periphery of the envelope between a first point and a second point of a perimeter within a plane perpendicular to the longitudinal axis, and - a pumping device adapted for inflating the second space to a control pressure greater than a pressure of the first space so that the envelope assumes a second shape by bringing the first and second points closer together, and for deflating the second space to a control pressure substantially equal to the pressure of the first space so that the envelope assumes a first shape that is different from the second shape said airship being characterized by the second space is delimited between a portion of the envelope and the wall, and the wall has a curvilinear length (c) less than or equal to a curvilinear length (a) of the portion of the envelope, in the plane perpendicular to the axis. - a flexible envelope without a rigid internal structure imposing a shape on the envelope, said envelope delimiting an inside space intended to be at least partially filled with a lighter-than-air first gas, extending along a longitudinal axis between a nose located at the front of the airship and a tail located at the back of the airship, and comprising an upper portion located at the top and a lower portion located at the bottom, said lower portion being opposite the upper portion, - a wall located inside the envelope, said wall being flexible, being gas-tight, extending longitudinally between the nose and the tail thus separating the inside space of the envelope into a first space intended to be filled with said first gas and a second space intended to be filled with a second gas, said second space being located on the periphery of the envelope between a first point and a second point of a perimeter within a plane perpendicular to the longitudinal axis, and - a pumping device adapted for inflating the second space to a control pressure greater than a pressure of the first space so that the envelope assumes a second shape by bringing the first and second points closer together, and for deflating the second space to a control pressure substantially equal to the pressure of the first space so that the envelope assumes a first shape that is different from the second shape the second space is delimited between a portion of the envelope and the wall, and the wall has a curvilinear length (c) less than or equal to a curvilinear length (a) of the portion of the envelope, in the plane perpendicular to the axis.