I checked the normals for the whole plane and found them all to be pointing out correctly. So I reversed the normals on the top part of the wing where the problem was occuring and the bump map rendered correctly. Go Figure?

I guess I might just invert that area's bump map from black to white, instead of reversing the normals on top of the wing.

Unless someone else has a suggestion to fix the problem. The rest of the plane's bump map is working fine.