Dirigibles, also known as airships or zeppelins, are lighter-than-air aircraft that use gas, such as helium or hydrogen, to achieve buoyancy. They have a large envelope filled with gas and are typically propelled by engines. Dirigibles can be steered and controlled, allowing them to travel long distances in the air. These vehicles were popular in the early 20th century for passenger travel and cargo transport. However, their use declined after accidents like the Hindenburg disaster in 1937. Today, dirigibles are mainly used for advertising, surveillance, and research purposes, offering a unique way to observe the world from above.