Because gas provides the lift in an airship or blimp, rather than a wing with an engine as in an airplane, airships can fly and hover without expending fuel or energy. Furthermore, airships can stay aloft anywhere from hours to days -- much longer than airplanes or helicopters. These properties make blimps ideal for such uses as covering sporting events, advertising and some research, like scouting for whales.
Recently, there has been renewed interest in using rigid airships for lifting and/or transporting heavy cargo loads, like ships, tanks and oil rigs, for military and civilian purposes. Modern airships, such as the Zeppelin NT and CargoLifter, use lightweight, carbon-composite frames that allow them to be huge, light and structurally sound. In addition to hauling cargo, airships may once again be used for tourism. So, the sight of a large airship moving across the sky may become more common in the near future.