List Headings in Navigation Panels

Hi All--
I'm wondering what you consider best coding practice for list headings in navigation panels.    
   - It would seem that <hx> would make the most sense, but adds a lot of clutter.   

   - tabindex="0" provides the advantage of focus and findability, but does not seem appropriate since it doesn't open or activate anything.   

   - <dl> doesn't seem right either, since the items in a list for nav are not definitions.   

   - Adding sections with headings seems even more cumbersome.
Example:
Planes <open/close>                                                                 Trains            Automobiles    |
Flying a Plane    Buying a Plane    Painting a PlaneThe BasicsThe ControlsThe Parachute
Suggestions? Many thanks.
Mike