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An airship or dirigible is a type of aerostat or lighter-than-air aircraft that can be steered and propelled through the air using rudders and propellers or other thrust mechanisms. Unlike aircraft that use aerodynamics, such as fixed-wing aircraft and helicopters that produce lift by moving an airfoil through the air, aerostatic aircraft stay aloft by having a large "envelope" filled with a lifting gas that is less dense than the surrounding air. In early dirigibles, the lifting gas used was hydrogen, despite widespread concern due to its flammability.

The alternative, helium, is nonflammable, but rare in most parts of the world. Large amounts of it were discovered in the United States. Thus, for a while, helium was rarely used for airships outside the United States.  All modern airships, made since the 1960s, have used helium.

The main types of airship are nonrigid blimps, semirigid airship, and rigid airship. Blimps are pressure airships where internal pressure, maintained by forcing air into an internal ballonet, is used to maintain both the shape of the airship and its structural integrity. Semirigid airships maintain the envelope shape by internal pressure, but have some form of internal support such as a fixed keel to which control and engine gondolas, stabilizers, and steering surfaces are mounted. Rigid airships have a structural framework which maintains the shape and carries all loads such as gondolas and engines. The framework contains numerous balloons, known as "gas cells" or "gasbags" which supply static lift without having to bear any structural loading. Rigid airships are often called zeppelins, as the type was invented by Count Zeppelin and the vast majority of rigid airships built were manufactured by the firm he founded.

Airships were the first aircraft to enable controlled, powered flight, and were widely used before the 1940s, but their use decreased over time as their capabilities were surpassed by those of aeroplanes. Their decline continued with a series of high-profile accidents, including the 1937 burning of the hydrogen-filled Hindenburg, and the destruction of the USS Akron. In the 21st century airships have been used in advertising, tourism, camera platforms for sporting events, geological surveys, and aerial observation - applications where the ability to hover in one place for an extended period outweighs the need for speed and maneuverability.


The first airship

The first person to make an engine-powered flight was Henri Giffard who, in 1852, flew 27 km (17 mi) in a steam-powered airship. Airships would develop considerably over the next two decades. In 1872, the French naval architect Dupuy de Lome launched a large limited navigable balloon, which was driven by a large propeller and the power of eight people. It was developed during the Franco-Prussian war, as an improvement to the balloons used for communications between Paris and the countryside during the siege of Paris, but was completed only after the end of the war.