American will give you a 20% bonus when you convert Marriott Rewards points to AAdvantage miles in October. No registration required.

They’ve offered this before, and indeed over the summer there was a 25% bonus for transferring hotel points generally to United miles (so inclusive of Marriott).

In general converting hotel points to miles is a poor deal — outside of Starwood — although if you need to top off an account it can make sense.

At a minimum, if you’re going to convert hotel points anyway then this bonus is better than not having the bonus.

The only reasonable use of this promotion is Marriott travel packages.

Packages are the most lucrative way to redeem Marriott points anyway and if you’re going to do that this makes American an attractive conversion partner.

Offer terms:

AAdvantage® Bonus Mile Offer Terms and Conditions
To qualify for this AAdvantage® bonus mile offer, member must initiate the AAdvantage mileage conversions with the Marriott Rewards® program between 12:00 am Central time October 1, 2015 and 11:59 pm Central time October 31, 2015 (the “Promotion Period”), and be in good standing AAdvantage Program and the Marriott Rewards Program. Members can convert multiple times during the Promotion Period.

To earn the 20% conversion bonus, member must convert points from the Marriott Rewards program. This offer is non-transferable and non-reversible.

Bonus miles will be posted by American Airlines to the qualifying AAdvantage member’s account within 7 business days after the initial conversion activity has been posted by Marriott Rewards. Bonus miles earned in this promotion do not count toward elite status qualification. American Airlines, AAdvantage, the Flight Symbol logo and AAdvantage Million Miler are trademarks of American Airlines, Inc.

(HT: Loyalty Lobby)