The motor vehicle comprising an aerodynamic underbody flap (1) rotating about a transverse axis (10) and a lower transverse structure (4) arranged at the rear of the lower part of a front bumper (6). The rear part of the lower transverse structure (4) comprises guide means (41, 42) which, in the event of a frontal impact, guide the backward movement of the lower transverse structure (4) such that the rear face of the lower transverse structure (4) comes into contact with the axis (10) of the aerodynamic underbody flap (1).