Software release development process, that we refer to as "release trajectory", involves development activities that are usually sorted in different categories, such as incorporating new features, improving software, or fixing bugs, and associated to "issues". Release trajectory management is a difficult and crucial task. Managers must be aware of every aspect of the development process for managing the software-related issues. Issue Tracking Systems (ITS) play a central role in supporting the management of release trajectory. These systems, which support reporting and tracking issues of different kinds (such as "bug", "feature", "improvement", etc.), record rich data about the software development process. Yet, recorded historical data in ITS are still not well-modeled for supporting practical needs of release trajectory management. In this paper, we describe a sequence analysis approach for modeling and analyzing releases' trajectories, using the tracking process of reported issues. Release trajectory analysis is based on the categories of tracked issues and their temporal changing, and aims to address important questions regarding the co-habitation of unresolved issues, the transitions between different statuses in release trajectory, the recurrent patterns of release trajectories, and the properties of a release trajectory.