Effective January 1, 2009, we are discontinuing the minimum mileage guarantee for non-elite status members for flights on American Airlines, American Eagle®, AmericanConnection®, oneworld® member airlines, AAdvantage® participating airlines as well as rail service and codeshare service booked under an AA flight number.

With this change, customers will earn AAdvantage miles equal to the actual distance flown or the applicable percentage* of the miles flown, and any associated bonuses will be calculated accordingly. Similarly, elite status qualifying miles and points earned for travel on eligible flights will also be based on the actual miles earned. A

Maybe this -- You used to get a minimum of X miles per segment flown, eg 500, but now it will be actual miles flown, so DCA-PHL will be 120 miles earned, not 500? Or if your category earns half, it would be 60 instead of 250. Just my guess.

Yes, that's exactly what it means.

Many short hops are less than 500 miles. So starting Jan 1, if the flight is less than 500 miles, the non-elites will earn the actual mileage flown, rather than a minimu of 500 miles.

Elites are exempted from this new rule.

Yeah, that knocks out my mileage between home & Puerto Rico.

Other airlines have already started doing this. Wasn't a stretch to think AA would join them sooner or later.