A system for mitigating an effect of an excitation of a structural flexible mode of an aircraft during flight, the aircraft comprising first and second flight control surfaces of different types, the system comprising: a pilot input device for receiving pilot input indicative of commands of one or more first flight control surfaces of the aircraft; and a controller operatively coupled to the pilot input device to receive signals indicative of the commands of the one or more first flight control surfaces of the aircraft, the controller comprising a memory having criterion programmed therein, the criterion comprising predetermined frequencies or command magnitudes susceptible of exciting one or more flexible modes of the aircraft, the controller being configured to: when a command of the one or more first flight control surfaces having a characteristic that will cause the command of the one or more first flight control surfaces to excite the structural flexible mode of the aircraft is received, cause the command of the one or more first flight control surfaces to be executed in conjunction with a command of one or more second flight control surfaces configured to mitigate the effect of the excitation of the structural flexible mode of the aircraft, characterized in that the mitigating command is of zero magnitude and duration if the pilot command is not susceptible to excite the structural flexible mode wherein the mitigated command is generated through application of transfer functions for applying criterion and wherein the command of the one or more first flight control surfaces is oscillatory and the characteristic is a predetermined frequency of concern for the command of the one or more first flight control surfaces. a pilot input device for receiving pilot input indicative of commands of one or more first flight control surfaces of the aircraft; and a controller operatively coupled to the pilot input device to receive signals indicative of the commands of the one or more first flight control surfaces of the aircraft, the controller comprising a memory having criterion programmed therein, the criterion comprising predetermined frequencies or command magnitudes susceptible of exciting one or more flexible modes of the aircraft, the controller being configured to: when a command of the one or more first flight control surfaces having a characteristic that will cause the command of the one or more first flight control surfaces to excite the structural flexible mode of the aircraft is received, cause the command of the one or more first flight control surfaces to be executed in conjunction with a command of one or more second flight control surfaces configured to mitigate the effect of the excitation of the structural flexible mode of the aircraft, characterized in that the mitigating command is of zero magnitude and duration if the pilot command is not susceptible to excite the structural flexible mode wherein the mitigated command is generated through application of transfer functions for applying criterion and wherein the command of the one or more first flight control surfaces is oscillatory and the characteristic is a predetermined frequency of concern for the command of the one or more first flight control surfaces. when a command of the one or more first flight control surfaces having a characteristic that will cause the command of the one or more first flight control surfaces to excite the structural flexible mode of the aircraft is received, cause the command of the one or more first flight control surfaces to be executed in conjunction with a command of one or more second flight control surfaces configured to mitigate the effect of the excitation of the structural flexible mode of the aircraft, characterized in that the mitigating command is of zero magnitude and duration if the pilot command is not susceptible to excite the structural flexible mode wherein the mitigated command is generated through application of transfer functions for applying criterion and wherein the command of the one or more first flight control surfaces is oscillatory and the characteristic is a predetermined frequency of concern for the command of the one or more first flight control surfaces.