No where in Rule 23 does the term "range lights" appear, but the two masthead lights, where fitted on larger vessels, do form a range similar to that established by two aids to navigation. This "range" helps in determining the orientation of a ship seen at a distance at night, the white masthead lights can be seen at a greater distance than the red and green sidelights.
a masthead light forward.
a second masthead light abaft of and higher than the forward one, except that a vessel of less than 50 meters in length shall not be obliged to exhibit such a light but may do so.
sidelights and a stern light.
A WIG craft only when taking off, landing and in flight near the surface shall, in addition to the lights prescribed in paragraph (a) of this Rule, exhibit a high intensity all-round flashing red light. WING-IN-GROUND CRAFT. A wing-in-ground (WIG) craft is defined as a vessel capable of operating completely above the surface of the water on a dynamic air cushion created by aerodynamic lift due to the ground effect between the vessel and the water’s surface. WIG craft are capable of operating at speeds in excess of 100 knots.