As a wing lifts a glider up, gravity pulls it down. However, pilots need to find constant upward forces to stay in the air for longer periods. Thermals, huge masses of rising warm air, are what hang gliders ride to stay aloft. These thermals are formed near Earth's surface and depend on warmth from the ground. Flat fields, dark pavement, and low lying towns create heat early in the day, while wooded areas heat up more slowly and stay warm longer.
Ridge lift is another power source.
While suspended in the harness system, the pilot steers a hang glider by shifting his or her center of balance. Leaning forward and backward causes the glider to dive or climb. This motion changes the angle of attack and is used to take off and land, as well as to control speed during the flight. Shifting from side to side causes the glider to bank into turns. Pilots use a control bar to move their weight in relation to the wings.