As the wings move forward, air is deflected above and below. When air speeds up, it drops in pressure, creating a low-pressure zone above the wing. This in turn gives the air traveling below greater relative pressure and the strength to push up the wing. To become airborne, a hang glider's airspeed must equal about 20 mph. Airspeed is a combination of the pilot's running speed and the speed of the wind coming toward the pilot.
Many different combinations are possible.
If a pilot is running at 20 mph, no wind is necessary. If the wind is blowing at 15 mph, the pilot need only run at 5 mph. A combination of a 10 mph wind with a 10 mph run is considered ideal. 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.