A Unit Load Device, or ULD for its acronym in English (Unit Load Device),[1]​ is a metal container or pallet used to load baggage, merchandise, and mail on wide-body aircraft and certain specific narrow-body aircraft. Allows a large amount of cargo to be grouped into a single unit. Since they involve fewer cargo units, they save time and effort for ground staff and help prevent flight delays.

Each ULD has its own list or "load manifest" so that its content can be controlled.

ULDs exist in two formats: pallets and containers.

Container manufacturers and airlines have developed different types for special products: such as those used to transport haute couture models, for household goods, etc. The most common types of unit load elements and their specifications are listed below.

The main advantage for using these unit load elements is economic. On the one hand, containerization reduces merchandise handling costs and on the other, the ULD rate is fixed and is much more profitable than the volume or weight rate (the maximum possible weight can be transported within the volume of the container).[4]​.

Another important advantage of using containers is time savings. Containers may be accepted for shipment later than merchandise that must be consolidated before shipment. A container can be picked up as soon as it is at the distribution center, while non-containerized merchandise must be ungrouped before pickup.

On the other hand, customs clearance of containers is faster since a container travels under a single air waybill" (air freight document).