What distance does a Glide Slope provide vertical guidance for in an ILS?

The Glide Slope in an Instrument Landing System (ILS) provides vertical guidance to pilots as they approach the runway for landing, ensuring that they maintain a proper descent angle. The Glide Slope typically operates within a certain distance from the runway threshold, which is conventionally maximized to about 10 nautical miles (NM). This distance is critical for pilots to receive accurate vertical guidance, allowing them to follow the intended glide path down to the runway.

In an ILS approach, the Glide Slope signal becomes increasingly important as the aircraft gets closer to landing, ensuring that pilots can adjust their descent rate effectively. The standard operational range of 10 NM aligns with ILS certification and operational guidelines, making it the correct answer in this context.