Many years ago an RAF Tristar lobbed into Edinburgh. Being ex-RAF and having nothing better to do I ambled across, introduced myself and asked for a look around. Going into the cockpit I showed off my new found knowledge of Autopilots by recognising the Para-visual display barber poles. “Oh” said I “PVD’s, your aircraft must be Cat IIIB capable.” “Yes” said the Captain “but the RAF only qualify us (the crew) to Cat II conditions so we don’t get poached by the Airlines.” I wonder if that is why they also made VC10 captains Squadron Leaders?
I was also told that Aircraft can be Cat IIIC capable but it is of little use as, if the conditions are that bad it is needed, the baggage handlers, refuellers and all those who meet the aircraft on stand will only find it by bumping into it!
Pedant mode on.
It is Cat I, II or III, capital I's. Not Cat 1, 2, 3 and certainly not 'Cat 111' as I saw in one travel agency window many years ago.
Pedant mode off.