1. A method for estimation of the speed of an aircraft relative to the surrounding air, of the angle of attack of the aircraft, and of the angle of sideslip of the aircraft, in a reference frame tied to the aircraft, comprising: using a vertical speed device on the aircraft to measure a geographical vertical speed of the aircraft; using a temperature probe on the aircraft to measure a temperature of air surrounding the aircraft; using a static pressure probe on the aircraft to measure a static pressure surrounding the aircraft; using a processor on the aircraft to: estimate an estimated static pressure on the basis of measurements of the geographical vertical speed of the aircraft measured by the vertical speed device, of measurements of the temperature of the surrounding air measured by the temperature probe, of reinitializations of the estimated static pressure, and of a feedback of the estimated static pressure, by integration over a vertical path of a hydrostatic equation; estimate a linear combination of a first intermediate variation of the speed of the aircraft relative to the surrounding air, of a first intermediate variation of the angle of attack of the aircraft and of a first intermediate variation of the angle of sideslip of the aircraft on the basis of a deviation between a variation of estimated static pressure and a variation of measured static pressure measured by the static pressure probe, the linear combination using coefficients calculated on the basis of the laws of local aerodynamic correction dependent on the aircraft, the speed of the aircraft relative to the surrounding air, the angle of attack of the aircraft, and the angle of sideslip of the aircraft, estimate a first indicator of quality of the linear combination estimated by the estimating the linear combination; estimate a second intermediate variation of the speed of the aircraft relative to the surrounding air, a second intermediate variation of the angle of attack of the aircraft and a second intermediate variation of the angle of sideslip of the aircraft, on the basis of inertial measurements, and of a feedback of the estimated speed of the aircraft relative to the surrounding air at output, of a feedback of the estimated angle of attack of the aircraft at output, and of a feedback of the estimated angle of sideslip of the aircraft at output, by likening the speed vector of the aircraft relative to the surrounding air to a speed vector of the aircraft relative to an inertial reference frame obtained by integration of the components of a measured acceleration vector (Inertial measurements), corrected for the kinematic effect of the reference frame tied to the aircraft and increased by the gravity projected into the reference frame tied to the aircraft; and consisting in estimating a second indicator of quality of the second intermediate variations; fuse the second intermediate variation of the speed of the aircraft relative to the surrounding air, second intermediate variation of the angle of attack of the aircraft, and second intermediate variation of the angle of sideslip of the aircraft respectively with the first intermediate variation of the speed of the aircraft relative to the surrounding air, first intermediate variation of the angle of attack of the aircraft, and first intermediate variation of the angle of sideslip of the aircraft, by filtering of least squares type weighted by the first and second indicators of quality or by a filtering of Kalman type; and of fusing the first and second indicators of quality into a fused indicator of quality on the basis of the error variance estimated by the filtering; perform a temporal integration of the fusion of the first and second intermediate variations, using reinitializations of the estimated speed of the aircraft relative to the surrounding air, of the estimated angle of attack of the aircraft, and of the estimated angle of sideslip of the aircraft; and generate an output for the operator of the aircraft so as to deliver at the output an estimated speed of the aircraft relative to the surrounding air, an estimated angle of attack of the aircraft, and an estimated angle of sideslip of the aircraft.