Abstract: A method and device are disclosed for determining the airspeed of a helicoper, in which, for a plurality of flight configurations of a calibration flight, magnitudes for estimating the airspeed and the collective P.sub.O and cyclic pitches P.sub.X and P.sub.Y of the lift rotor, the pitch P.sub.Z of the antitorque rotor, the angles of bank .theta..sub.X and .theta..sub.Y and the acceleration .gamma..sub.Z are measured. Correlation matrices between the speed estimated with respect to the air and variables related to the pitches, angles and acceleration measured during the calibration flight are then formed. Formulae are derived, for calculating the estimated speed, by a stepwise regression algorithm, which are used in normal flight for calculating, in response to the pitches, angles and acceleration measured during normal flight, the speed with respect to the air, if required after correction of the values of the multiplicative coefficients of these calculation formulae.