Through June 15, 2007, American Airlines customers who purchase an airline ticket at AA.com with their MasterCard are automatically entered to win the Ultimate Baseball Fan’s prize package that includes a grand prize of a $15,000 MasterCard gift card which can be used towards baseball tickets, hotel stays and more; $10,000 in American Airlines gift cards for the winner and a guest to travel from their hometown to baseball-crazed cities such as San Francisco, Boston, New York and Chicago plus a premium baseball gift bag, courtesy of MasterCard. Customers can enter without a purchase by registering at http://www.aa.com/promo and forwarding the sweepstakes information to four other people. You’ll have to move fast to enter this sweepstakes ending June 15.