Glider refers to a fixed-wing aircraft that is heavier than air and does not rely on power devices to fly. After take-off, they only rely on the reaction of air to their lifting surfaces to fly freely, and most of them have no power devices. It can be towed by plane, winch or car, sliding up and down a high slope into the air. In the absence of wind, the glider relies on its own gravity component to gain forward power in its downward flight; In the updraft, the glider can fly horizontally or ascend like an eagle spreading its wings.