What are the ILS systems primarily used for?

The ILS (Instrument Landing System) is specifically designed to provide precise instrument approaches to runways, ensuring that aircraft can land safely and accurately in various weather conditions, especially when visibility is limited. The system consists of two main components: the localizer, which provides lateral guidance to line the aircraft up with the runway centerline, and the glide slope, which offers vertical guidance to ensure the aircraft descends at the correct angle.

This advanced system is crucial for helping pilots execute landings safely when they cannot rely on visual references alone. Its primary function is to assist during the critical phase of the flight as the aircraft approaches and lands on the runway.

The other options involve different aspects of aviation. Visual guidance during daylight may use other systems, taxiway navigation is generally managed through ground control instructions and visual aids, and airborne navigation away from airports typically relies on GPS and other navigation systems rather than ILS. Thus, the correct answer focuses specifically on the ILS's integral role in supporting instrument approaches, underlining its importance in aviation safety and efficiency.