A series of _______ make up an RNAV route.

An RNAV (Area Navigation) route is defined by a series of waypoints. Waypoints are specific geographic locations defined by a set of coordinates which allow aircraft to navigate efficiently along a predetermined path. These waypoints can be either terrestrial landmarks or points established by navigational data. In the context of RNAV, these points enable pilots and air traffic controllers to manage air traffic more effectively by facilitating more flexible routing that does not rely solely on traditional airways or navigational aids.

While navaids, checkpoints, and horizons are terms relevant to navigation, they do not specifically describe the structure of an RNAV route. Navaids generally refer to ground-based electronic aids that assist in navigation, checkpoints may be informal reference points used for situational awareness, and horizons generally refer to the visible line that separates Earth and sky, which is not directly involved in the definition of a route. Therefore, waypoints are the correct term to denote the elements that compose an RNAV route.