Method for determination of a rigid value of an aerodynamic coefficient of an aircraft, in which measurements are made in a wind tunnel on a model of the said aircraft and, on the basis of these measurements, at least one value, known as flexible model value, of this aerodynamic coefficient is determined, characterized in that a rigid value of the aerodynamic coefficient is calculated on the basis of the said flexible model value(s) and a correction taking into account the flexibility of the model. A plurality of flexible model values is determined on the basis of measurements made by varying the parameter q/E and maintaining the angle of incidence at a constant value, and the correction consists in an extrapolation operation providing a value of the aerodynamic coefficient corresponding to q/E=0. As a variant, a single flexible model is determined and the correction consists in adjusting the said value with the aid of a correction factor.