Solar-powered high-altitude long endurance aircraft that harvest and store solar energy can fly indefinitely if they are able to close a 24-hour energy cycle. Perpetual endurance is possible when energy consumption does not exceed energy storage. The trajectory taken determines the net change in energy. A trajectory-generation algorithm is necessary to plan for self-sufficiency. The algorithm must be fast enough to run in real-time to be useful for trajectory planning. Traditionally, efficient trajectories are computed using optimal control methods. Since they are computationally slower than real-time, they cannot be used for in-flight planning. We present a greedy heuristic solution based on a multi-path variation of Dijkstra’s shortest path algorithm that runs much faster than real-time.