Re: Ticket classes
There is indeed an IATA resolution on class usage but some of the definitions are quite generic like "economy discounted". For some selling classes it's vital to follow the resolution particularly where interline sales are made and for others it's not that important. The main alliances tend to agree class usage together to aid interline selling, codeshare and the like.
Airlines are different: my airline uses F A Z // J C D I U // W T P // Y B H K M R V N L S Q O G X E for selling classes in order highest/lowest!