I am trying to design an Model Airplane wing component.   I have lofted the wing with success.   Then I have sketched a spline on the upper surface of the part.  On another plane I have sketched a spline on a predefined plane.  When I try to loft from the spline-on-a-surface to the other spline, I get an error.  I am attaching the part with another loft above the wing.  Ideally I would make one contiguous loft but the loft is having difficulty between the wing and the upper loft.  I have made it work in surfaces, but I do not get the results I want. Here is a link to the file.   I would greatly appreciate it if someone could help me.