Categories of Instrument Landing Systems (ILS) The ILS is categorized into three different categories: CAT I, CAT II, and CAT III. CAT III is further divided into three subcategories: CAT IIIa, CAT IIIb, and CAT IIIc. Each category has specific requirements and limitations regarding visibility and decision heights (DH). CAT IIIb and CAT IIIc allow […]