Abstract: An air guide device, especially an extendable and retractable rear spoiler on a motor vehicle, with an adjustable air guide element and at least one, also adjustable, flow element designed as an underflow guard. The flow element is designed as a component separate from the air guide element and is connected to it by an adjusting mechanism.

Abstract: An air guide device for a motor vehicle, especially a rear spoiler, which can be moved between a retracted, nonoperating position and an extended, operating position and comprises an air guide body, on which two lateral air guide body sections, which can be moved in the transverse direction of the vehicle, are arranged. It is provided that the contours of the bottom surfaces of the lateral air guide body sections facing the vehicle conform to the cooperating external vehicle contour at least when the these air guide body sections are in the operating position.