Streamlining piece for vehicle bumper

The fairing part has a plastic wall (21) fixed on the structure (5) of a motor vehicle and defining an air pipe side under a bumper. The wall is formed with rigidifying ribs (23) extending from the front edge and over the length of the wall. An impact cross member (35) with an alveolar structure is integrated to the wall and has a hollow metallic beam (37). Impact absorption blocks (25) are connected to the wall through frangible parts.