"Invite up to 5 people to fly Northwest Airlines and you can earn up to 20,000 Bonus Miles when they travel by May 31, 2005 with Refer-A-Friend. Heres how it works:

-Register up to 5 friends to participate in the Refer-A-Friend promotion.
-The first time each friend does one of the activities listed below, you'll earn the associated Bonus Miles. If all friends complete each of the activities, you'll earn a total of 20,000 Bonus Miles.
-Each time one of your friends does one of the activities listed below, they'll also earn the associated Bonus Miles. There's no limit to the Bonus Miles they can earn during the promotion period!"