What Is ILS? Definition & Meaning in Aviation
ILS (instrument landing system) is a ground-based radio system that guides an aircraft down to a runway using a horizontal and a vertical beam.
In plain language
It lets aircraft land in low cloud and poor visibility, down to limits set by the ILS category. Without it, pilots need to see the runway earlier on the approach.
Example
In foggy weather, an airport with a suitable ILS can keep landing aircraft when one without it would have to close.
Why it matters
The ILS is the main reason flights can keep landing in poor visibility. When fog hits, airports and airlines with better instrument approaches keep operating longer than those without.