A 3.25 * 103-kg aircraft takes 12.5 min to achieve its cruising altitude of 10.0 km and cruising speed of 850 km/h. If the plane's engines deliver, on the average, 1500 hp of power during this time, what is the efficiency of the aircraft engines? I initially believed the power out would be: (Kinetic energy + Potential energy)/Time And efficiency would be 1500hp/power out. But after my calculations, I got 14.6% efficiency, when it should be 48.7% efficiency. What did I do wrong?