Unit Load Devices (ULDs) are nearly always required to be approved for use, that is to say, certified for continued airworthiness by the relevant Civil Aviation Authority (CAA). That’s because, just like any other aircraft component, ULDs have to be robust enough to cope with all likely and extreme circumstances during flight (e.g. when the aircraft accelerates and decelerates, banks, climbs and descends or hits air pockets or turbulence). Under such severe circumstances, a certified ULD ensures the cargo does not move around the hold, endangering the aircraft’s structure and systems, because it is locked to the hold’s floor.
It must be noted that the certification process is conducted solely between the ULD manufacturer and the applicable regulatory authorities such as FAA (Federal Aviation Administration in the USA) and EASA (European Aviation Safety Aviation in Europe).