A flight control method for a rotary-wing aircraft, said aircraft following a path T sol relative to the ground at a forward speed Va, a longitudinal direction X extending from the rear of said aircraft to the front of said aircraft, an elevation direction Z extending upwards perpendicularly to said longitudinal direction X, and a transverse direction Y extending from left to right perpendicularly to said longitudinal direction X and elevation direction Z, said aircraft comprising: - at least one rotary wing provided with a plurality of main blades (111, 112, 113), the collective pitch and the cyclic pitch of which are variable about a pitch axis, said aircraft being capable of performing movements in rotation about said directions X, Y, Z and in translation in said directions X, Y, Z, - an autopilot which generates control commands in accordance with predefined modes of operation and in accordance with flight setpoints, said control commands being capable of causing said movements of said aircraft in rotation and/or in translation relative to said directions X, Y, Z, and - flight commands comprising at least one control member (31, 32) which is provided jointly with a plurality of movement axes A, B, C, D, characterised in that - a first operating mode of said control members (31, 32) and of said autopilot is applied when the longitudinal speed U X of said aircraft is greater than a first threshold speed V threshold1, said longitudinal speed U X being a projection of said forward speed Va onto said longitudinal direction X, said autopilot then enabling said aircraft to fly while maintaining path relative to the ground, said flight setpoints of said autopilot being a ground course angle TK sol, said forward speed Va, a slope P and a heading ψ, and - a second operating mode of said control members (31, 32) and of said autopilot is applied when said longitudinal speed U X is less than a second threshold speed V threshold2, said first threshold speed V threshold1 being greater than said second threshold speed V threshold2, said autopilot then enabling said aircraft to fly while maintaining heading, the flight setpoints of said autopilot being said longitudinal speed U X, a lateral speed V Y, a vertical speed W Z and said heading ψ. - at least one rotary wing provided with a plurality of main blades (111, 112, 113), the collective pitch and the cyclic pitch of which are variable about a pitch axis, said aircraft being capable of performing movements in rotation about said directions X, Y, Z and in translation in said directions X, Y, Z, - an autopilot which generates control commands in accordance with predefined modes of operation and in accordance with flight setpoints, said control commands being capable of causing said movements of said aircraft in rotation and/or in translation relative to said directions X, Y, Z, and - flight commands comprising at least one control member (31, 32) which is provided jointly with a plurality of movement axes A, B, C, D, - a first operating mode of said control members (31, 32) and of said autopilot is applied when the longitudinal speed U X of said aircraft is greater than a first threshold speed V threshold1, said longitudinal speed U X being a projection of said forward speed Va onto said longitudinal direction X, said autopilot then enabling said aircraft to fly while maintaining path relative to the ground, said flight setpoints of said autopilot being a ground course angle TK sol, said forward speed Va, a slope P and a heading ψ, and - a second operating mode of said control members (31, 32) and of said autopilot is applied when said longitudinal speed U X is less than a second threshold speed V threshold2, said first threshold speed V threshold1 being greater than said second threshold speed V threshold2, said autopilot then enabling said aircraft to fly while maintaining heading, the flight setpoints of said autopilot being said longitudinal speed U X, a lateral speed V Y, a vertical speed W Z and said heading ψ.