System for measuring and evaluating air and inertial data of an aircraft for indirectly estimating at least one incidence angle α and one skidding angle P with respect to a relative wind direction Wn of said aircraft, comprising: - at least one pressure measuring system (19, 21) adapted to directly or indirectly detect at least values of dynamic pressure q c and possibly of static pressure p s; - at least one accelerometric measuring system adapted to directly measure at least axial values n y of inertial acceleration of said aircraft with respect to a pitch axis Y of said aircraft; - processing means adapted to compute and provide: - at least one preliminary estimated value α̃ of said incidence angle α; - at least one preliminary estimated value β̃ of said skidding angle β, were β̃ = f(q c, n y) characterized in that: - said at least one accelerometric measuring system is adapted to directly measure possibly n z with respect to a yaw axis Z of said aircraft; - the system further comprises at least one inclinometric measuring system adapted to measure or compute the values θ of an attitude angle of a roll axis X of said aircraft with respect to the horizon; and - said processing means are adapted to compute and provide the at least one preliminary estimated value α̃ of said incidence angle α, where α̃ = f(q c, θ, VS) and/or α̃ = f(q c, n z), where VS is at least one Vertical Speed value computed by said processing means depending on said values of static pressure p s. - at least one pressure measuring system (19, 21) adapted to directly or indirectly detect at least values of dynamic pressure q c and possibly of static pressure p s; - at least one accelerometric measuring system adapted to directly measure at least axial values n y of inertial acceleration of said aircraft with respect to a pitch axis Y of said aircraft; - processing means adapted to compute and provide: - at least one preliminary estimated value α̃ of said incidence angle α; - at least one preliminary estimated value β̃ of said skidding angle β, were β̃ = f(q c, n y) characterized in that: - said at least one accelerometric measuring system is adapted to directly measure possibly n z with respect to a yaw axis Z of said aircraft; - the system further comprises at least one inclinometric measuring system adapted to measure or compute the values θ of an attitude angle of a roll axis X of said aircraft with respect to the horizon; and - said processing means are adapted to compute and provide the at least one preliminary estimated value α̃ of said incidence angle α, where α̃ = f(q c, θ, VS) and/or α̃ = f(q c, n z), where VS is at least one Vertical Speed value computed by said processing means depending on said values of static pressure p s. - at least one preliminary estimated value α̃ of said incidence angle α; - at least one preliminary estimated value β̃ of said skidding angle β, were β̃ = f(q c, n y) - said at least one accelerometric measuring system is adapted to directly measure possibly n z with respect to a yaw axis Z of said aircraft; - the system further comprises at least one inclinometric measuring system adapted to measure or compute the values θ of an attitude angle of a roll axis X of said aircraft with respect to the horizon; and - said processing means are adapted to compute and provide the at least one preliminary estimated value α̃ of said incidence angle α, where α̃ = f(q c, θ, VS) and/or α̃ = f(q c, n z), where VS is at least one Vertical Speed value computed by said processing means depending on said values of static pressure p s.