Until June 15, WorldPerks members can earn a free coach-class certificate after completing just three roundtrips on qualifying fares to any Northwest or KLM worldwide destination. All qualifying travel must originate or terminate in the 50 United States or Canada.

The free certificate is good for travel within the 48 contiguous states or between the 48 contiguous states and Canada. For Hawaii and Alaska residents, the certificate is good for travel between Hawaii or Alaska and the 48 contiguous states. Free travel must take place between Sept. 1, 2004 and June 15, 2005. Participants can earn a maximum of two free travel e-certs.

Advance registration is required, and must be completed by April 15.

The offer is in addition to Northwest’s “Fly to Europe, Fly Free” promotion, which offers a free ticket to travelers who fly to Europe in business or first class.