An aircraft including at least one engine having counter-rotating rotors, the engine or at least one of the engines having imbalances associated with at least one ellipse. The aircraft includes at least one vibration damper attached in an arrangement such that, at a given engine speed and for at least one given common direction of a large axis of the ellipse or at least one of the ellipses, a speed related to the two ends of the damper is higher than for any other arrangement of the damper.