This document discusses travel inequality and why some travel startups fail. It notes that according to research, most people only travel 1-2 times per year, while a small percentage of frequent travelers are responsible for a large portion of airline revenue. The document advocates that for startups to be successful, their business models and retention tactics need to target different types of travelers based on frequency, from one-time users to frequent travelers who subscribe. It provides a framework for matching business models and retention strategies to types of travelers based on their trip frequency.