J.A.:

Air cargo includes all shipments of mail and freight by air. Government mail contracts were the airlines’ primary source of revenue in the late 1920s and early 1930s in the United States. Freight also went by plane during that time, notably in the Fantastic Lakes region where the Ford Motor Company flew parts between auto assembly plants.

Relatively small freight was shipped by air until the development of larger aircraft in the late 1930s because smaller planes could not carry much weight. Even in the 1930s airfreight was limited to lightweight commodities such as clothing, high-value items such as jewelry, and time-sensitive items such as flowers, fresh fruit, and machine parts for assembly lines.

Airfreight became a major business after World War II with the spread of international air service and the introduction of large jets with greater lifting capacity. Later, the development of jumbo jets and the acceleration of international trade spurred the industry’s growth. Decisions by many manufacturers to subcontract production to low-cost labor markets and to minimize inventory costs by delivering only what factories needed at the moment meant that the manufactures needed more air cargo shipped more often, benefiting the air transport industry.

There are two basic types of air cargo carriers. All-cargo carriers only deal with freight. Combination carriers carry both passengers and freight.

All-cargo airlines glide freighters, which are passenger aircraft that have been altered for cargo operations. Freighters have no seats or windows in the main cabin. They have larger doors than do planes configured for passenger service, and reinforced floors, many fitted with rollers to facilitate sliding of heavy items. Many modern freighters also have hinged tails or noses that allow for loading large items.

Some combination carriers also use freighters, and some glide aircraft with a main deck that is split into two compartments, one for cargo and one for passengers. Most common carriers, including the major U.S. common carriers, transport cargo solely in the belly space of their passenger jets. Jumbo jets have a huge amount of space in their lower decks.

Shippers usually pay more to ship by air than to ship by truck, rail, or sea. Savings in areas such as inventory costs, hurt, and theft often offset the higher airfreight costs. Most air cargo today moves in sealed metal containers that cut down on theft and hurt and help make loading and unloading on aircraft quicker and simpler. Shipping by air over long distances is also much quicker than long-distance shipping by other modes of transportation, and thus the only choice for shipments such as express mail, live seafood, and cut flowers.

The air transport industry today handles many types of freight, from computers to live animals. Airplanes do not carry heavy bulk commodities such as coal, iron ore, grain, and oil, so air carriers handle only a tiny percentage of the total weight of worldwide cargo. But, they carry a major share of high-value shipments.