An instrument runway served by IlS to and along the surface of the runway and:
- for CAT IIIA – intended for operations with a decision height lower than 100 ft, or no decision height and an RVR not less than 200 m
- for CAT IIIB – intended for operations with a decision height lower than 50 ft, or no decision height and an RVR less than 200 m, but not less than 50 m
- for CAT IIIC – intended for operations with no decision height and no RVR limitations.