A ULD, or unit load device, is either an aircraft container or an aircraft pallet with its net, used to group cargo, baggage and mail into a single unit that locks into an aircraft hold. Air cargo moves in ULDs because a loaded unit can be built away from the aircraft, weighed and planned in advance, and loaded in minutes rather than piece by piece.
The part most people outside the industry miss is that a ULD is not packaging. IATA classifies every ULD as a removable aircraft part, subject to civil aviation authority requirements across design, testing, production, operation, repair and maintenance. An airworthy ULD has to restrain its load and protect the aircraft structure and systems in flight.
Around 1 million ULDs are in service worldwide, with a replacement value above USD 1 billion.
What Is a ULD in Air Cargo?
A ULD is a device for grouping, transferring and restraining cargo in transit by air. It takes one of two forms, a container with its own structure and door, or a flat pallet onto which cargo is built and then secured with a net.
Both forms do the same job. They turn a collection of separate pieces into one standard unit that the aircraft’s cargo loading system can accept, lock down and carry safely.
The unit is built before it reaches the aircraft. That is the whole point. Building away from the aircraft cuts turnaround time, allows weight and balance to be planned in advance, and means the load arriving at the aircraft door is already a known quantity.
Why Are ULDs Treated as Aircraft Parts?
ULDs carry flight safety consequences, which is why they sit under airworthiness rules rather than packaging standards. A unit that fails in flight can shift, damage aircraft systems or compromise the structure.
IATA makes a point that is unusual in aviation. ULDs are the only aircraft parts that leave the airline’s control, pass through many unregulated hands, and then return to the aircraft. A container might be built by a shipper, moved by a forwarder, handled by a ground services provider and stored at a terminal before it goes anywhere near an aircraft again.
Certification comes from the aviation authorities. Approval by EASA or the FAA establishes that a design is airworthy, and units manufactured in the United States are built to the relevant FAA Technical Standard Order.
What Are the Main Types of ULD?
ULDs divide into containers and pallets, and within each, into standard and specialist units.
The table below sets out the types most commonly seen in air cargo operations and what each one is used for.
| Type | Form | Typical use |
|---|---|---|
| AKE, widely called the LD3 | Container, contoured lower deck | The most common lower-hold container on wide-body aircraft |
| AMA | Container, main deck | Large main deck container on freighter aircraft |
| PMC | Pallet | The standard main deck and lower deck pallet, used for most general palletised cargo |
| PAG | Pallet | Smaller standard pallet, common on lower decks |
| RKN | Active temperature controlled container | Pharmaceutical and other temperature sensitive cargo, maintaining its own internal temperature |
| Horse stalls and livestock units | Specialist container | Live animal transport under the live animals regulations |
| Car and vehicle units | Specialist pallet | Vehicles and heavy or irregular loads |
Pallets are cheaper to operate than containers and handle large, heavy or awkwardly shaped loads that would not fit inside a fixed shell. Containers protect their contents fully, close with a door, and suit smaller mixed consignments.
Temperature controlled units sit in a category of their own, because an active container maintains its internal temperature independently for a sustained period. How that affects pricing is covered in our guide to chargeable weight in air freight, and the wider handling requirements in temperature controlled air freight.
What Do ULD Codes Mean?
Every ULD carries a code that identifies what it is, what shape it is and who owns it. The code is built from a three-character prefix, a serial number and an owner code.
- The first character identifies the category, for example a certified aircraft container or a certified aircraft pallet
- The second character identifies the base dimensions
- The third character identifies the contour and compatibility, which determines the aircraft types the unit fits
- The serial number identifies the individual unit
- The final two or three characters identify the owner, usually an airline or a leasing company
So a unit marked AKE followed by a serial and an owner code is a certified aircraft container, on a specific base size, with a contour that suits lower-hold positions on wide-body aircraft, belonging to a named operator. Contour codes are allocated through IATA’s ULD Board.
Who Sets the Standards for ULDs?
ULD standards come from IATA, built on the regulatory requirements of ICAO and national civil aviation authorities. The IATA ULD Regulations, known as the ULDR, bring the technical and operational requirements together in one manual.
The ULDR covers four things.
- Regulatory requirements from ICAO, national authorities and the aircraft weight and balance manual
- Minimum specifications for design, testing, performance and manufacture, aligned to IATA, ISO and SAE standards
- Operational guidance covering serviceability checks, build-up and break-down, transport, transfer and storage
- Training requirements and standards
The standards themselves are developed by the IATA ULD Board, which works alongside ISO, SAE, Airports Council International, EASA, the FAA, the Civil Aviation Administration of China and FIATA, the international federation of freight forwarder associations.
Who Is Responsible When a Shipper Builds Its Own ULD?
When a shipper or freight forwarder builds a ULD, they take on responsibility for a component that affects flight safety, and the airline remains accountable for accepting it. This arrangement is known as the Bulk Unitization Programme, or BUP.
Shipper-built units reduce handling time at the cargo terminal, because a consignment arrives already unitised rather than needing to be built from loose freight during air cargo handling. The trade-off is that the build quality, load distribution, restraint and net tension are set by someone outside the airline’s direct supervision.
IATA has published guidance on Bulk Unitization Programme quality and standards for the freight forwarding community, which reflects how much of the ULD chain now sits outside airline control. Most ULD handling is outsourced to ground service providers, and demand for shipper-built units continues to grow.
For a forwarder, three things matter most.
- Only build on units you are authorised to build on, and check serviceability before loading
- Respect the contour, because a unit built beyond its profile will not fit the aircraft position it was planned for
- Net and restrain to the specification, since a correctly loaded unit with a poorly fitted net is still a rejected unit
What Does Poor ULD Handling Cost the Industry?
Repair and loss of ULDs costs the industry an estimated USD 330 million each year, before counting aircraft damage, flight delays and cancellations caused by ULD problems. IATA’s safety campaign targets a reduction of around USD 475 million in industry costs.
The underlying problem is inconsistency. Training requirements, operating standards and handling practices vary enormously across the industry, from excellent to non-existent, while the units themselves move continuously between airlines, handlers, forwarders and shippers.
Questions About Unit Load Devices
What does ULD stand for?
ULD stands for unit load device. It covers both aircraft containers and aircraft pallets with their nets, used to group and restrain cargo, baggage and mail for carriage by air.
What is the difference between a ULD container and a ULD pallet?
A container is an enclosed unit with its own structure and door, and it protects its contents fully. A pallet is a flat base onto which cargo is built and secured with a net, and it handles larger, heavier or irregular loads that would not fit inside a container.
What is an LD3 container?
The LD3 is the common name for the AKE, a contoured container designed for the lower hold of wide-body aircraft. It is the most widely used lower-deck container in air cargo.
What is an RKN container?
An RKN is an active temperature controlled container. It maintains its own internal temperature independently for a sustained period, which makes it suitable for pharmaceutical and other temperature sensitive shipments.
Are ULDs certified?
Yes. ULDs are removable aircraft parts and require airworthiness certification. Approval by EASA or the FAA establishes that a design meets the required standard, and units remain subject to serviceability checks throughout their working life.
Can a shipper build its own ULD?
Yes, under the Bulk Unitization Programme. The shipper or forwarder builds the unit, and the airline remains responsible for accepting it, which is why IATA publishes build quality guidance aimed specifically at the forwarding community.
