The present invention relates to an air flap (10) for an air-ducting device, in particular a vehicle heating, ventilation and/or air-conditioning system, with at least two ducts (2, 4), which have a common outlet zone, comprising a region (12) which allows part of the outlet zone to be divided in a sealed manner in each position of the air flap (10), the region (12) being smaller than the area of the air flap.