Originally Posted by
MSPeconomist
I would disagree with this example. While C isn't unrestricted last seat availability, it's generally in most markets a fully flexible and fully refundable without penalty business class fare, unlike the D I Z fares that generally have change fees (typically ranging up to about $500 for TATL/TPAC RTs exUSA, but this depends on the market) and generally aren't refundable (as a credit to the original means of payment).
Moreover, some I fares have advanced purchase and minimum stay requirements while C fares generally do not.
Well I would be cautious about any generalization regarding what rules might typically apply to a specific booking code. For example, I see two "I" fares on JFK-LHR for travel 1-Mar-20 through 7-Mar 20, and both are fully refundable. I see at least one C fare for travel in June that has a change/cancel fee of $450/500. And I even see a J fare with the same penalties. It's really the specific fare rules that determine the restriction, there's nothing inherent in the booking code/fare class, and things can change all the time. Bottom line, the only reason a flyer really cares about the booking code is for mileage earnings, and as mentioned, for DL-marketed business class it's all the same except J earns 2x MQMs. For partners there could be more nuances & differentiation for MQMs and MQDs.