Northwest Airlines is one of the world's largest carriers. Along with their travel partners, they serve more than a 1000 cities in more than 160 countries on six continents. With that much global reach, they have a lot of loyal customers. But their 25-year-old loyalty program wasn't yet reaching their customers online. Epsilon helped Northwest Airlines build a dynamic online program backed by a powerful segmentation strategy. They're achieving outstanding ROI and gaining more frequent fliers for their next 25 years.