Cargo (or freight) is goods or produce transported, generally for commercial gain, by ship, aircraft, intermodal train, van, or truck. In modern times, containers are used in most intermodal freight transport.
Air cargo, commonly known as air freight, is collected by firms from shippers and delivered to customers. Aircraft were first used for carrying mail as cargo in 1911. Eventually, manufacturers started designing aircraft for other types of freight as well. There are many commercial aircraft suitable for carrying cargo such as the Boeing 747 and the bigger An-124, which was purposely built for easy conversion into a cargo aircraft. Such large aircraft employ quick-loading containers known as "unit load devices (ULDs)", much like containerized cargo ships. The ULDs are located in front section of the aircraft. Most nations own and utilize large numbers of cargo aircraft, such as the C-17 Globemaster III, for their logistical needs.
Trains are capable of transporting large numbers of containers that come from shipping ports. Trains are also used for the transportation of steel, wood, and coal. They are used because they can carry a large amount and, generally, have a direct route to the destination. Under the right circumstances, freight transport by rail is more economical and energy efficient than by road, especially when carried in bulk or over long distances. The main disadvantage of rail freight is its lack of flexibility. For this reason, rail has lost much of the freight business to road transport. Rail freight is often subject to trans-shipment costs, since it must be transferred from one mode of transportation to another. Practices, such as containerization, aim at minimizing these costs. Many governments are currently trying to encourage shippers to use trains more often because of the environmental benefits. Many firms, such as Parcelforce, FedEx, R+L Carriers, and U-Haul, transport all types of cargo by road. Delivering everything from letters to houses to cargo containers, these firms offer fast, sometimes same-day, delivery. A good example of road cargo is food, as supermarkets require deliveries every day to keep their shelves stocked with goods. Retailers of all kinds rely upon delivery trucks, be they full-size, semi trucks or smaller delivery vans.