Landing is the most dangerous phase of the entire flight phases. If the total loss of thrust occurs during flight, a powered aircraft converts to a glider, which can use kinetic and potential energy only. For this reason, a proper scheme is needed for safe landing in cases of the total loss of thrust. This paper presents three-dimensional unpowered auto-landing guidance based on trajectory generation, expanding the concept of the energy-to-range ratio. We develop the terminal velocity estimation method for a horizontal plane applied to three-dimensional space; this method is based on the previously suggested terminal velocity estimation method for a vertical plane. Then, we show trajectory generation for landing guidance combining vertical with horizontal waypoints. The proposed auto-landing guidance with trajectory generation is evaluated by numerical simulation.