unit load device (ULD) is a pallet or container used to load luggage, freight, and mail on wide-body aircraft and specific narrow-body aircraft. It allows a large quantity of cargo to be bundled into a single unit. Since this leads to fewer units to load, it saves ground crews time and effort and helps prevent delayed flights. Each ULD has its own packing list (or manifest) so that its contents can be tracked.

The most important purpose of a ULD is to secure cargo during flight. The safety of the plane and its passengers comes first every time.

ULD also allows:

  • eliminate the need for manual loading and unloading 
  • protect cargo contents so that goods arrived undamaged
  • maximise the use of the aircraft’s cargo space
  • the fast and easy transfer of cargo between planes in transit

To prevent the ULDs moving around during flight and potentially damaging the aircraft, the plane has loading and restraint systems. These interface directly with a ULD, effectively locking the ULD into place so it becomes part of the aircraft.