For suitably equipped aircraft, different ILS Facility Performance categories are mentioned as below:- 

(i) Cat I Operation: A precision instrument approach and landing with a decision height not lower than 60m (200ft) and with either a visibility not less than 800m or a runway visual range not less than 550m.

(ii) Cat II Operation: A precision instrument approach and landing with a decision height lower than 60m (200ft) but not lower than 30 m (100ft) and a runway visual range not less than 350m.

(iii) Cat III Operation: Different CAT III operation are further subdivided into:-

(a) CAT IIIA Operation: A precision instrument approach and landing with :- 

   a) a decision height t lower than 30m (100ft) , or no decision height; and

   b) a runway visual range not less than 200m.

(b) Cat IIIB Operation: A precision instrument approach and landing with :-

   a) decision height t lower than 15m (50ft), or no decision height; and

   b) runway visual range less than 200 m not less than 50m. 

(c) Cat IIIC Operation: A precision instrument approach and landing with no decision height and no runway visual range limitations. 

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