The rules that use the category "<location_mod>" are:

<airspace_clearance-recursive>

<clearance_verb> <airspace_entry_mod> <location_mod>

<item-not_call_sign>

<det-sing> <item_n-sing> <location_mod>

<item_n> <location_mod>

<airspace_clearance>

<clearance_verb> <airspace_entry_mod> <location_mod>