Originally Posted by traveler18

Also Starwood offers a 5,000-mile bonus when you transfer 20,000 Starpoints to miles

Originally Posted by Brobbel

http://webflyer.com/programs/mileage...rter/index.php
The other path, through Starwood, gives less:

American Express Membership Rewards (US) converts to (starting) 10,000
Starwood Preferred Guest (at a ratio of 999:333) converts to 3,330
American AAdvantage (at a ratio of 1:1) Total: 2,500

Using the bonus when converting a block of 20,000 points will give you 3,250 miles for each 10,000 points.