[R.W.Dale]

In aeronautics there's really two kinds of drag

Induced drag and parasite drag

Everything related to induced drag would be load bearing this is the drag from the airfoil form

Parasitic drag could be load bearing. But it can also not be any more complicated than keeping air out of cowlings and spaces. Or not installing some thing onto the fuselage that protrudes into the slipstream. It is actually OK to use tape on commercial aircraft in some of these instances

A good example on our cars would be anything perpendicular to the airflow will need to be rigid enough to not flutter which would be worse than it not being there

Anything parallel to the airflow like a wheel skirt also doesn't need to flutter but at the same time sees much lower aerodynamic loads