Definition
Precision instrument approach procedures that use the Instrument Landing System to provide pilots with electronic lateral guidance (localizer) and vertical guidance (glide slope) to a specific runway. ILS approaches allow aircraft to descend to a published decision altitude in low-visibility conditions, at which point the pilot must have the required visual references in sight to continue to landing or otherwise execute the missed approach.
Plain English
Landing approaches that use radio signals to guide the aircraft down a precise path to the runway -- one signal keeps the wings lined up with the runway centerline, and another keeps the aircraft on the correct descent angle. The pilot follows these signals down until they can see the runway and land, or until they reach a set altitude where they must go around if the runway is not in sight.
Context Anchor
Seen in instrument flying, approach briefings, approach charts, and air traffic control clearances such as “cleared ILS approach.”
Derivation
“Approach” comes from older words meaning “to come nearer.” In aviation, it does not just mean getting closer to an airport; it means the planned final part of the flight that leads toward landing.
Why Pilots Care
They allow safe landings in fog, rain, or low clouds, directly improving safety and keeping flights on schedule.
Intuition Check
Do not read “approach” here as simply “coming near the airport.” An ILS approach is a specific published procedure that uses Instrument Landing System guidance to lead the aircraft toward landing.
Example Sentence 1
With the ceiling at 400 feet and visibility one mile, the crew briefed the ILS approach to Runway 27.
Example Sentence 2
During training the instructor had the student track the localizer and glideslope on successive ILS approaches.