> ## Documentation Index > Fetch the complete documentation index at: https://docs.canadava.com/llms.txt > Use this file to discover all available pages before exploring further. # CAT > Category (ILS Approach) This glossary is written for **virtual airline and flight simulation** use within Virtual Air Canada Airline. It is not intended as a real-world aviation reference. Category (CAT) refers to the classification system for ILS (Instrument Landing System) precision approaches, defining the minimum weather conditions under which a specific approach may be conducted. The categories are based on two key parameters: Decision Height (DH) or Decision Altitude (DA) - the point at which the crew must either have adequate visual reference to continue or initiate a missed approach - and Runway Visual Range (RVR), which measures forward visibility along the runway surface. The standard categories are: CAT I, with a DH no lower than 200 ft and RVR of at least 550 m (or visibility of 800 m); CAT II, with a DH between 100 and 200 ft and RVR of at least 300 m; CAT IIIa, with a DH below 100 ft and RVR of at least 175 m; CAT IIIb, with a DH below 50 ft (or no DH) and RVR of 50-175 m; and CAT IIIc, which requires no DH and no RVR limitation (full autoland in zero-zero conditions, rarely certificated in practice). Each higher category requires more sophisticated ground equipment, aircraft systems (such as certified autoland capability and fail-operational flight control), and specific crew training and currency. ## In Virtual Airline Operations At Virtual Air Canada Airline, CAT I approaches are the standard for most operations. CAT II and III approaches require specific aircraft certification and crew training that would be documented in a real operator's Operations Specifications. In the simulator, flying a CAT II or III ILS to minimums is a useful proficiency exercise - pay attention to the lower decision heights, the reliance on autoland systems, and the importance of a stable, on-speed approach well before the decision point. ## Related Terms * [DA/DH](/aops/additional-resources/glossary/da-dh) - Decision Altitude/Decision Height * [BDRT](/aops/additional-resources/glossary/bdrt) - Both Dependent Runway Thresholds * [CDA](/aops/additional-resources/glossary/cda) - Continuous Descent Approach