What is inventory?

American Airlines has various inventory buckets. These “buckets”, or fare codes, dictate what is available to be purchased or how many upgrades are available on a particular flight. Every flight is different.

A fare class chart from 2019 can be found here. This chart explains different buckets, their tiers, and what they’re used for.

For upgrades, the main inventory bucket used for economy to business is C. Note that AA has begun to also use C for revenue tickets. Read more on how to find availability here.

For revenue, each flight has a certain amount of each inventory bucket. As cheaper inventory buckets are sold, only more expensive (“full fare”) buckets are left.