A new method for analyzing multi-segment trajectories is presented. The new method solves the equilibrium equations iteratively and in the same way for each type of segment. The method requires an aerodynamic model, a propulsion model, and the segment trajectory specified in altitude and velocity coordinates. No small angle assumptions are made in the equilibrium equations and the trajectories are always continuous.For a given point spacing of the trajectory, the numerical integration of fuel weight is more accurate than previous methods. Encapsulating the equilibrium equation solution allows the rapid development of new segment types. The benefits of this new method are assessed by comparing with current practice.