In order to integrate an aerodynamic box without a solid shim, a spar joint is provided. The spar joint comprises a first spar having a first spar contact surface and a second spar having a second spar contact surface. When the first and second spars are fixed to each other, the first and second contact surfaces engage each other in a manner forming a contact plane. The first and second contact surfaces are inclined such that a first imaginary plane that is an extension of the contact plane in a chordwise direction forms at least one intersection with a second imaginary plane that is originating from a chordwise extremal end of an aerodynamic skin. The spar joint is used in aerodynamic boxes, such as flap boxes and TE boxes. The spar joint is also used in airfoil profiles.