gas is still used in airships to provide lift.
Hydrogen used to be used in airships.
Hydrogen was once used to fill airships. Quite dangerous due to how flammable it is.
Hydrogen and helium are two elements that are kinda-sorta interchangeable in airships.
Hydrogen
Helium is typically used to fill airships and balloons due to its low density, which allows them to float in the air.
because hydrogen used to be in those airships and since hydrogen is flammable it was very dangerous
Modern airships use Helium for lift which is non-combustible whereas in the past airships such as the Hindenburg used Hydrogen for lift which is highly combustible. In addition, modern airships take advantage of new alloys and polymers which give them a much stronger airframe.
In 1937, the Airship Hindenberg crashed in a raging fireball as it was landing from it's journey from Frankfurt to New Jersey. 36 people were killed and the cause of the explosion is still unknown.after this event, the world did not feel safe flying in zeppelins any more, and the giant airships were no longer used as passenger craft.
It shut down the Nazi airship program and ended all research into using airships in commercial passenger service.
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.
Airships were often used to carry freight and passengers. But became unpopular after the advent of jets and other types of aircraft because they are slow. Initially they used fuel which made them highly flammable when accidents occured.