Cathay Pacific Asia Miles - C J

I just noticed in the CX downloadable flight planner that J is actually referred to as "Premium Business Class" and C as "Business Class". What exactly is the reason for two different full-fare (?) biz tickets. Most airlines seem to do without.

Once upon a time many years ago, CX calls their Business Class, "C". But as fares have changed, CX's fare codes changed as well. It's now "J".

So in the eyes of CX, a "C" class fare is not full fare Business Class whereas "J" is. Case in noting is when you are trying to endorse a ticket over to CX. CX will look at the fare code of the carrier and insist that C means "Full Fare Economy upgraded to Business". Take for example, SQ flying between SFO-HKG. SQ uses C class , and when endorsing over to CX, you can be sure that CX will insist that you pay a surcharge even though the IATA fares are exactly the same.

tks gb. As far as I remember I was always offered a First Class lounge pass when buying a J ticket TPE-HKG at the airport. With a TA-bought C class ticket they would only let me in the business lounge.
I also just found out that BA have exactly the same J and C classes, also called "Business Class Premium".