American Airlines has expanded the number of domestic fare classes eligible for corporate discounts, effective immediately. The new structure applies to all customers that have corporate contracts with American; those customers do not have to wait for their contract renewals, according to the airline.

Air carriers group their byzantine fare classes into buckets for corporate discounts. In American's buckets, "Full" fares are eligible for higher corporate discounts than "Applicable" fares. Applicable fares, in turn, are eligible for higher corporate discounts than "Upper Loyalty" fares, which are eligible for higher discounts than "Lower Loyalty" fares. The actual discount for each bucket depends on each corporation's contract with the carrier.

American's new domestic discount structure is at left. The carrier has added its P, A, D and I fare classes, making them eligible for corporate discounts for the first time. P, A, D and I fares generally refer to those that come with instant upgrades to business or first class. They are now in the same bucket as Applicable fares, which generally are the uppermost classes of fares that cost less because they're nonrefundable or are restricted in other ways. American has moved L class fares, which are discount economy, into that bucket, as well. L Class fares had been in the Upper Loyalty bucket.

S fares have moved from the Lower Loyalty bucket to the Upper Loyalty level. And American's deeper-discount O class has become eligible for corporate discounts for the first time.

American estimates that its corporate customers will save a combined tens of millions of dollars a year as a result of the new structure. They also will get credit for more volume, as well, now that more classes are eligible for discounts.