Question
The solicitation for this card states no annual fee if "the mileage cap is shared".
What does that mean?
Answer
I surmise it means that if you already have a AAdvantage Mastercard you may also request an AAdvantage American Express card for no additional fee, but you will still be subject to the annual mileage cap specified in the terms and condtions of the Mastercard.
For example "The maximum number of AAdvantage® miles you can earn with the Citi® Platinum Select® / AAdvantage® World MasterCard® is 100,000 AAdvantage® miles per calendar year (purchases recorded on your Jan.-Dec. billing statements). " You would still be subject to the 100,000 mile limit unless you paid the annual fee for the American Express version.