Don't know about "J", but all airlines (including the one I work for) use "C" and for as long as I'm alive, I have always seen "C" as the letter for business class... (Economy=Y, Business=C, First=F)
It’s an IATA standard thing, but the first letter (denoting class of service) of the fare basis code is known as the ‘prime code’. Typically, J refers to a ‘business premium’ fare while C is a ‘business’ fare. Hence the letters being used interchangeably by those who aren’t airline staff. (for the record, B is an economy-class fare.) These definitions are old though, before the creation of premium economy sections, or something as elaborate as Etihad’s The Residence. I’m not sure if they’re still used in the original forms as I only have the text of the IATA 2007 ticketing manual.
It's an IATA standard thing, but the first letter (denoting class of service) of the fare basis code is known as the 'prime code'. Typically, J refers to a 'business premium' fare while C is a 'business' fare. Hence the letters being used interchangeably by those who aren't airline staff. (for the record, B is an economy-class fare.) These definitions are old though, before the creation of premium economy sections, or something as elaborate as Etihad's The Residence. I'm not sure if they're still used in the original forms as I only have the text of the IATA 2007 ticketing manual.
The standard that I know of is: F for First. J/C for Business. W for Premium Economy such as on Turkish or Aeroflot. Y+ for extra legroom only Economy Plus on carriers such as United. Y for Economy.