Northwest Airlines has brought back its “Mile-A-Rama” promotion for the winter.

The promotion is a perennial favorite with WorldPerks members, as it essentially rewards the typical behaviors of business travelers.

Once registered, members have a variety of options to earn points. Flying Northwest, booking at nwa.com, signing up for MCI service, staying at a partner hotel or renting a car from a partner all qualify for various levels of points. At the end of the promotion, the points are tallied, then converted to WorldPerks miles.

Flying on Northwest, for example, can earn up to 150 points. When March rolls around, those 150 points will convert to 4,500 miles.

The caveat: different WorldPerks members seem to be eligible for different levels of points. Oddly enough, it seems that the least frequent flyers are offered more points, while the sky-bound elites are offered less. For example some members are offered 10 points for checking in online, while others can get 15 points. Visit online and enter you membership number to see where you stand.

Theories (conspiracy and otherwise) abound, but many believe that the promotion is intended to both drive the business of the less frequent flyer as well as to pick up a few extra email addresses from members who may not be registered for Northwest’s email services (most elites already are, and the rules specify that the members email account must be active through Feb. 2004).

Qualifying activities can be completed until Feb. 29. You must register at http://www.nwa.com prior to completing any qualifying activities but not later than Jan. 31. The offer is not retroactive.