Front diffusers are provided on a front underbody covering of a vehicle, in a manner lying laterally on the inside next to the two front wheel houses. Each front diffuser has a longitudinally directed air duct integrated into the front underbody covering and has a pivotable flap. The flap is connected to an actuating device that can be actuated by a switch in the passenger compartment for shifting the device between a first position flush with the outer skin and a second upwardly pivoted position. The second, upwardly pivoted position of the front diffuser or of the flap produces an increase in downforce at the front axle.