Which of the following describes the term "interval" in aircraft positioning?

The term "interval" in aircraft positioning refers specifically to the distance maintained between two landing aircraft. This concept is crucial in aviation to ensure safe separation during the landing process. By maintaining an appropriate interval, air traffic controllers and pilots can prevent potential collisions and manage traffic effectively, particularly in busy airspace or during landing sequences. This distance is a critical component of flight safety, allowing for timely adjustments and ensuring that each aircraft has enough space to land without interference from the preceding aircraft.

The other options address various aspects of air traffic and aircraft operation but do not define the term "interval" specifically. Ensuring that all aircraft remain within visual range, for instance, is more about situational awareness rather than the spacing between them. Similarly, the time it takes to cross the landing threshold and the speed at which aircraft arrive focuses on different operational factors that do not relate directly to the measure of distance that "interval" conveys.