Airships are huge balloons with propellers to drive them, and they were once used to carry as many as 200 passengers.
The airships were filled with hydrogen, a light gas. However, hydrogen is also inflammable. There were several disasters in which airships caught fire, and they disappeared by the end of the 1930s.
However, airships are now flying again, but they are not common. They are lifted by helium gas, which does not catch fire.
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