modern hot air ballooning

Modern hot air ballooning involves using a specially designed inflated envelope, or "balloon," to lift a passenger basket filled with people. The balloon is heated by a burner that burns fuel, typically propane, to produce hot air. Because hot air is less dense than cold air, it causes the balloon to rise. Pilots control altitude by adjusting the air temperature — heating to ascend and allowing the air to cool or venting to descend. Modern materials and safety features make hot air ballooning a regulated and enjoyable form of aerial navigation, often used for recreation, sightseeing, and competitive events.