An aerodynamic device for attachment to a trailer of a tractor-trailer having a centerline, a trailer sidewall and a trailer door. The aerodynamic device comprises an airfoil and a flexible mounting system. The airfoil comprises a leading edge, a trailing edge, an inner surface, and an outer surface. The flexible mounting system comprises a door hinge, a mounting bracket, a trailer hinge and a door strap. The door hinge is coupled to the trailer door. The mounting bracket is coupled to the inner surface of the airfoil. The trailer hinge is coupled to the mounting bracket and the trailer sidewall. The door strap coupled to the door hinge at a first end and the mounting bracket at a second end.