Master Planning is currently the dominant approach to airport strategic planning. However, history shows that this approach can often result in costly mistakes. Because there are many stakeholders with conflicting objectives, deep uncertainty about the future, and many potential strategies, planners often narrow their scope by using a single forecast for the future, leaving out alternative strategies, and excluding stakeholders, resulting in a Master Plan that quickly becomes obsolete and may be opposed by some stakeholders. What is needed is a flexible, integrated approach that enables collaboration among stakeholders. Such an approach can be facilitated using a Decision Support System (DSS) that provides a way for decisionmakers and stakeholders to evaluate alternatives quickly and easily with respect to their outcomes of interest. We present the conceptual design for a DSS called HARMOS, showing how it meets the high-level requirements for airport strategic planning while addressing the problems associated with Master Planning.