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During a winch launch, a glider is pulled by a wire cable like a kite, raising it to an altitude of around 1000 ft (300 m). For the rest of its flight, being un-powered, the heavier-than-air aeroplane is always falling. However a pilot can gain height by circling within a strong thermal — a column of air that is rising at a faster rate than the plane is falling. On a good day, an experienced pilot can travel hundreds of miles before landing.