Difference between Z and C class ?
 

Both are business class, but a difference in price. Any idead what's the difference ?

Both are business class tickets, but from different fare buckets. There is no actual difference between the service one would get. Or at least not that I know of.

One of the fare is discounted, and I believe that and assume that Z is the discounted business class fare because for the majority of the airlines, Z is discounted fare. On certain airlines, such as United, they only give 100% miles for Z class tickets.

On most airlines, C fares are fully changeable, fully refundable walk-up fares, while Z fares are typically non-changeable, non-refundable, advance-purchase fares. This is the case with SQ.

Mostly true, however, SQ uses Z as the prime booking codes for LAX/EWR-SIN nonstops. Those are the most flexible fares on those routes.

Any idea why?

Hrrm... on my recent AMS-SIN return leg, I was waitlisted on my C fare ticket but confirmed on a Z class seat which would have required an $800 top up and $150 ticket reissue fee. Luckily the C fare seat cleared a few days before my flight.

Z and C are both business fare. If you start originally from CGK then C is discounted fare and Z is full business fare. Out of CGK if you hold C class then you are able to have 1 stop over on the inbound flight and Z you can have both inbound and outbound stop over. Out of SIN Z is discounted fare and C is the highest.

To differentiate different fares for different routings. For example, there are plenty of LAX-SIN C and J fares out there but none of them allow the nonstop. So it seems SQ chose Z for the fares which apply to the nonstop. Why Z? I have no idea. :)

From the horse's mouth (or rather, email address):

We offer 5 types of booking class on our business class service as follows:
(1) C - is full fare business class booking class
(2) J - is business class fare with restriction/s booking class
(3) D - is business class round-the-world booking class, and selected Interline Sales
(4) I - is business class redemption booking class
(5) Z - is business class on A345 non-stop flight between Singapore-Los Angeles, and vv.

OK, I'm on SG-EWR route, that explains.

Can anyone clarify if Z is strictly for the A345 flights? Just like the way SQ intends to only put R class on the A380? Apparently, from yelsmana post, you can get Z out of CGK, which I understand is not a A345 destination other than the 2 daily A345 flights.

That's false.

Z class is available for all entire flights out of CGK. It is not true that Z class only available on A345.

I think there is some confusion here. Z class is on the A345 longhaul. Because pax flying those flights may be connecting to or from other flights, the same booking class is made available on other flights. However Z cannot be booked for an itinerary that doesn't include an A345 longhaul flight. The alternative approach (used by some airlines) is to specify in the fare rules that Z (or whatever) is an upsell for certain flights, and the other connecting flights allowed in the fare book into another class. There are advantages and disadvantages of each approach.

False. Booking classes vary by airlines. There is a good summary for *A airlines in the *A forum sticky.

Flying United in Z class and crediting to Mileage Plus only earns 100% miles. But business class bonus is earned when crediting to some other FFPs. Likewise, Z class flying some other airlines may earn differently. There are no absolutely common classes in terms of fare type/earning rates/etc.