Which factor makes the difference between a 3D-RNAV system and a 4D-RNAV system?

In the context of RNAV (Area Navigation) systems, the distinction between 3D-RNAV and 4D-RNAV lies primarily in the concept of time management in addition to the standard three dimensions of navigation (latitude, longitude, and altitude).

A 3D-RNAV system navigates in three dimensions: it calculates the horizontal (2D) position and retains altitude information for navigation. However, it does not account for the time aspect of the flight path. In contrast, a 4D-RNAV system incorporates time as the fourth dimension. This means it not only focuses on the aircraft's spatial position in three-dimensional space (latitude, longitude, and altitude) but also includes time as a critical factor for managing the aircraft's flight path.

This inclusion of time allows for more sophisticated route management and scheduling, enabling the aircraft to adhere to specific time constraints along its route as part of its performance, which is essential for maintaining efficiency and meeting air traffic control requirements. Thus, the understanding of how to integrate and navigate through these four dimensions is vital for modern air navigation systems, especially with the increasing demand for airspace utilization and precision flying.

Consequently, the presence of time management as a factor justifies the differentiation between