The invention relates to a ventilator flap, making up the terminal part of a main air duct providing an upstream air flow (3), said ventilator flap being provided with diffusion means, directing means, and control means for going from one mode to the other which comprises a central duct (5), at least partly coaxial to an annular duct (8), the two ducts (5, 8) having the upstream ends thereof (2) connected to the principal air duct and each having, at the downstream end thereof, one of said diffusion and directing means and a control bush (12), which may be displaced between a first position, in which the above serves to close a connection between the central duct (5) and the annular duct (8) and a second position in which the above serves to open said connection.