Air transport and pipelines

Air transport is the fastest mode, but it is costly, so it carries mostly passengers and light, valuable or perishable goods. It can reach inaccessible places (mountains, deserts, ice fields) where no road or railway can go, and it has great strategic value in war and emergencies.

Building and running airports needs very costly infrastructure, so air transport is most developed in industrialised countries.

The world's air routes form a dense east-west belt in the Northern Hemisphere, with the densest networks in the eastern USA, western Europe and south-east Asia. The Southern Hemisphere has far fewer routes, because it has fewer people, less land, and fewer economic activities.

Pipelines carry liquids and gases steadily and cheaply over long distances: water, petroleum, natural gas, liquefied coal, and even milk, which is carried in pipelines from farms to factories in New Zealand.

In the USA, the Big Inch pipeline carries petroleum from the oil wells of the Gulf of Mexico to the north-eastern states. About 17% of all freight in the USA moves by pipeline. India, too, has major oil and gas pipelines.