An aeroelastic modelling of an axisymmetrical airship is discussed in this paper. The main difficulty is due to the fact that instabilities are not axisymmetrical. Furthermore an Euler-Lagrange kinematical coupling is necessary in order to represent the fluid-structure interaction. Our strategy is based on some arbitrary change of domain (for the air flow) which are governed by the movement of the structure. Some numerical results illustrate the method.