Southwest Airlines is cel­e­brat­ing four years of LUV in Denver with a spe­cial pro­mo­tion for Colorado Customers. Beginning today, Southwest is offer­ing its Colorado Customers a free flight when they book a Business Select fare to/from Denver. The offer is valid for both new and exist­ing Rapid Rewards Members for travel booked by Jan. 31, 2010, and travel com­pleted by Feb. 28, 2010 (see terms and con­di­tions below). Colorado Residents who aren’t yet Rapid Rewards Members can join and be auto­mat­i­cally reg­is­tered for the pro­mo­tion. Simply enroll in the pro­gram via the link below before com­plet­ing qual­i­fy­ing travel.