A problem of the flow around a rectangular wing under the transonic buffet conditions in a wind tunnel is investigated numerically and experimentally. It is shown that a three-dimensional flow with a “mushroom" structure of the surface streamlines on the wing surface is formed instead of a close-to-two-dimensional flow in the case with self-excited oscillations along the streamwise coordinate (buffet). For the purpose of buffet control, an ejector is proposed, which provides boundary layer suction from the upper surface of the wing and jet ejection at the trailing edge of the wing. The spectral analysis of the experimental pressure oscillations on the upper surface of the wing shows that the proposed device effectively suppresses pressure oscillations at the buffet frequency.