Earn up to 100,000 WorldPerks bonus miles for completing mileage-earning activities at Northwest Airlines. Register at http://www.nwa.com/offers/mysterymiles by Dec. 31, 2007 and complete as many of the 19 activities as you can by Jan. 31, 2008. The link to this promotion is expected to go live in the middle of September, so check back later if you aren’t able to register. We expect this promotion to be similar to Northwest’s recent Perkology promotion where members could earn bonus miles for completing qualifying mileage partner activities such as applying for and using the WorldPerks co-branded credit card, using mortgage and real estate partners, signing up for wireless service, staying in partner hotels, renting a car, purchasing a cruise, buying miles or shopping through WorldPerks’ online mall.