Finsup72

You're specifically looking for C class for an immediate upgrade. If you see C availability pop-up, immediately call AA and ask for them to process the upgrade. However, it's highly likely you will not see any availability at all or you won't see availability until T-36 hours till departure. "I" class is discounted business and will dwindle first as people buy business class tickets. As you see "I" and "D" buckets dwindle down to 0, "J" is full-fare business and represents the number of seats left for sale. For example, if you see J7 at T-36, there's a good chance your upgrade has already processed or you'll see C availability open up. If you see J2 or J3, it's unlikely they will process an upgrade until you're at the gate. If you see J0, it means they are not selling any business class tickets for a variety of reasons - coach is oversold, business is sold out, etc. It's never good to see J0 if you're hoping for an upgrade but there are some instances where they will still process upgrades (no shows, upgrade from J to F, oversold coach, etc.)