Originally Posted by natbread

CX shows booking class just before you confirm your booking. When on the payment webpage, choose all your flights, then it should prompt you with all the status points etc. Click "show more" (or similar i forgot the exact wording) then it should show Class x under the equipment listed to operate the flight.

For Econ Light, Essential, Flex etc, they do not affect the fare class. They only affect the fare basis (the 8 digit code that most people don't know what it means). For example, Econ Light shows as xx21xxxx and Econ Flex shows as xx41xxxx. You could buy Fare Class Q with Econ Flex and that would still be considered discount economy. HOWEVER, Econ Flex does affect the amount of status points you earn, which can be seen either during purchase or from the status point calculator on the CX webpage.

On the topic of fare classes, I'm not 100% sure but I think its as follows:
S,N,Q,O: Discount Economy
M,L,V: Economy
Y,B,H,K: Full Economy

Let me know if any of this doesn't make sense or if anyone more experienced can provide a better explanation.