helium, mostly
Airships are usually the shape of a oval. They look like blimps. Airships are usually filled with helium to keep them afloat.
Hydrogen was the gas that was once used to filled airships. It is extremely plentiful and easy to produce. However, it is also extremely flammable and caused a few accidents. Helium is now used.
Zeppelins.
==Zeppelin Airships== They were called Zeppelins, after their designer Count Ferdinand von Zeppelin.
German zeppelins
Using hydrogen in airships is considered dangerous because hydrogen is highly flammable and can lead to explosions if exposed to air. This risk was famously demonstrated by the Hindenburg disaster in 1937, where an airship filled with hydrogen caught fire and crashed. As a result, helium is now the preferred gas for use in airships due to its non-flammable nature.
Zepplins
Helium is a lighter gas than oxygen, ever seen balloons filled with helium? They rise upwards with heat due to a lesser amount of particles. If we used oxygen, the airships wouldn't get off the ground!
In their early history, buoyant airships (zepellins, blimps) were filled with hydrogen, a highly flammable gas. Since the Hindenburg disaster, hydrogen has been supplanted by helium, a much more expensive material, but one that is inert and hence much safer.
The most famous airships are Hendenburg and Zeppelin.
Airships do use gas, to provide lift.
It was hydrogen. That's why it caught fire. Modern airships use helium.