What is the function of a Standard Terminal Arrival Route (STAR)?

The function of a Standard Terminal Arrival Route (STAR) is to move aircraft into terminal airspace efficiently. STARs are pre-defined routes that guide aircraft from the en-route phase of flight to the approach phase when they are landing at an airport. These routes are designed to streamline the flow of arriving traffic and reduce congestion in busy terminal airspace. By providing a structured route, STARs help with the safe and efficient management of air traffic, allowing for a smoother transition for aircraft as they approach their destination.

The use of STARs also aids air traffic controllers by providing a consistent and predictable flight path for arriving flights, which simplifies their workload and enhances safety. Unlike alternate flight paths, which serve a different purpose related to emergency situations, or departure routes, which are used when leaving an airport, STARs specifically address the arrival phase. Additionally, while ensuring that aircraft are visually visible can be important for safety, it is not the primary function of STARs; rather, they depend primarily on instrument flight rules (IFR) rather than visual references.