<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by JIMBOLIGUY:
"A" class is a special class. "A" class is only sold in certain markets and does reprsent the "sticker" upgrade class -- that is X class on 2-Class service planes.
Basically, "A" class is a coach fare (usually priced the same as full-Y), but allows a free upgrade to first if space is available. In some ways, I think it is similar to a YUP fare.
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Class A *used* to be the sticker upgrade class, and the YUP-like "discounted" First Class. Sticker upgrades are now in X class [and according to SABRE watchers, X appears as available inventory 100 hours before departure].
A is now the First Class booking code for: upgrades using miles (or a VIPOW when the ticket contains intercontinental legs), and paid round-the-world tickets in First.