THE GEOGRAPHY OF TRANSPORT SYSTEMS

Source: Wikipedia.
Unit load devices (ULD) come in several dimensions and are designed to fit the bellyhold of a jet plane, particularly wide-bodied aircrafts. The number of containers that can be fitted is a function of the length of the cargo area. The loading of ULD is rather simple as it involves rolling in the container. 32 such ULD can be loaded in a 747-400.