Southwest Airlines has been successful due to its principal values, creation of a unique culture, and business model focused on operational simplicity and low costs. Some strengths that have contributed to its success include having a friendly approach with customers, innovative retention strategies, and a strong work culture. However, the airline is dependent on a single airplane producer and faces threats from increasing costs and competition from other carriers offering similar low-cost services. Overall, Southwest has created a memorable brand focused on customer service through strategies like empowering employees and building relationships.