I’m not sure about the USA but this promo is very popular with Aussies and I have been watching for it since last month!  We can collect Amex Membership Rewards and transfer them to SPG at a 2MR = 1 SPG ratio, then transfer them onwards to AAdvantage to get award tickets which in most cases have no fuel surcharges.

40,000 Australian Amex MR = 20,000 SPG

20,000 SPG = 25,000 American AAdvantage miles

I got a lot of free AA miles last year which helped me book the award tickets in J class from Windhoek to Brisbane for next year’s trip!  Starwood will be merging into Marriott later this year so I doubt this promo will be back next year so take AAdvantage of it while you have the chance!