You confirmed that the STL file and the wing surface in the Fluent mesh have the same shape. You won’t use the STL file at all. The mesh file can be used to simulate airflow around the wing without the use of the STL file. In fact the .cas file is better because it has the fluid properties, inlet boundary conditions, outlet boundary conditions and the other boundary conditions at the other faces of the air domain, as well as the turbulence model etc. to allow you to do simulations in Fluent at other conditions.