Category I/II/III

Category I, II, and III (CAT I/II/III) is the ICAO classification system for precision approach and landing operations. Each category defines the minimum decision height and runway visual range (RVR) at which a pilot must have visual reference to continue the approach to landing.

• CAT I: Decision Height (DH) not lower than 200 ft (60m) and RVR not less than 550m (or visibility 800m). Standard ILS minimums used by most airlines worldwide
• CAT II: DH not lower than 100 ft (30m) and RVR not less than 300m. Requires enhanced aircraft systems, special crew training, and improved approach lighting
• CAT IIIA: DH not lower than 50 ft (15m) and RVR not less than 175m
• CAT IIIB: DH lower than 50 ft (or no DH) and RVR not less than 50m. Requires autoland capability
• CAT IIIC: No DH and no RVR limitation — true zero-zero operations. Theoretically defined but not yet operationally implemented anywhere

Higher categories require progressively more sophisticated aircraft equipment, airport infrastructure (lighting, taxiway guidance), and crew qualifications.