Hanggliders are always sinking thorough the air. However if the air they are flying in is rising as fast or faster than their sinking speed they stay aloft. You can do this near cliffs or hills where the wind is blowing up their side. Many pilots prefer to fly inland where giant bubbles of warm air rise into the sky like invisible balloons. Hanggliders turn in the rising air and sometimes travel for hundreds of kilometers by flying from one thermal to the next.