What Is CAT III? Definition & Meaning in Aviation
CAT III is the most demanding category of instrument landing, allowing aircraft to land in very low visibility, with runway visual range as low as about 200 m down to 50 m or less depending on the sub-category.
In plain language
It needs a runway with a suitable ILS and lighting, a certified aircraft and a specially trained crew. Many aircraft can then land automatically.
Example
In fog season, flights to airports and runways equipped for low-visibility operations are more likely to keep operating than those without.
Why it matters
CAT III explains why some flights keep landing in thick fog while others are diverted. The difference often lies in the runway’s equipment and the aircraft and crew approvals.