Lighter than air Aircraft

A device sustained in the air by aerostatic lift. Balloons and dirigibles are examples of lighter-than-air aircraft made of materials that are heavier than air, but are filled with a gas (or with hot air) that is less dense than the surrounding air. When a gas-filled aircraft displaces a greater weight of air than it weighs, aerostatic lift is produced, and the aircraft rises into the air.

Aircraft that can rise and remain suspended by using contained gas weighing less than the air that is displaced by the gas.