No, you could probably (that doesn't mean you can't) not use the miles you got on the outbound to upgrade the return. The reason is that upgrades with miles on CO require that you order a certificate and present it at check in or ticketing.

BUT, if a nice agent realizes that you will get the miles and lets you have a negative balance......

Link to Chase:
Main C/C page: http://creditcards.chase.com/homepage_frame.html

CO Card: http://creditcards.chase.com/Product...ntinental.html