A Unit Load Device — a ULD — is a container or pallet used to load cargo as a single unit onto an aircraft, so a whole batch of shipments moves, is weighed, and is tracked as one piece of equipment instead of dozens of loose cartons. Every ULD carries an identifier, and once you know how to read it, ULD codes stop looking like random letters and start telling you exactly what the equipment is. This guide breaks the code down piece by piece, with worked examples like AKE and PMC, and shows where those codes turn up on the air waybill and manifest.
The IATA ULD identification code has three parts. First come three letters that describe the equipment. Then a serial number, usually four to five digits, that makes the individual unit unique. Then a two-to-three character owner code, normally the IATA code of the airline that owns or registers the unit. Read together, a full identifier looks like AKE 12345 AB: the type code, the serial, and the owner. The three letters are the part worth learning, because they carry the meaning.
The anatomy of a ULD code
Each of the three letters does a specific job. Together they pin down the equipment's category, its footprint, and its shape — three facts in three characters:
- First letter — type / category. What kind of ULD it is. A is a certified aircraft container, P is a certified aircraft pallet, and D is a non-certified (forkable) container. Other category letters exist for more specific equipment.
- Second character — base size code. The footprint dimensions of the unit — the floor area it takes up in the aircraft hold or on the ramp.
- Third character — contour / compatibility code. The shape of the unit and which decks and positions it fits, since a lower-deck hold and a main-deck position accept different contours.
With , you can capture ULD identifiers straight off the paperwork — the type, base, and contour read exactly as printed, so the wrong equipment never slips in from a transposed character.
Start hereWorked examples: AKE and PMC
Two of the most common ULD type codes in air cargo show the pattern clearly. AKE is the familiar LD3 lower-deck container: A for a certified aircraft container, K for its base size, E for its contour. PMC is the workhorse 96 × 125 inch certified pallet: P for pallet, M for the 96 × 125 inch base, C for its contour. Same idea, different equipment — the letters carry it.
Because the type code is compressed, small differences matter. Two codes that share a first letter can be very different pieces of equipment once the base and contour change, and the loadmaster plans weight and position around exactly those differences. That is also why the code is worth reading precisely rather than skimming: the whole meaning lives in three characters, so a single wrong character points at the wrong equipment.
Containers, pallets, and certification
The first letter also tells you the broad family the unit belongs to. A ULD is either a container — an enclosed box, sometimes with a door or a fabric side — or a pallet, a flat platform whose cargo is built up and held down with a net or a rigid igloo shell. Containers and pallets are both ULDs; the type letter is what separates them at a glance, before you ever see the size or contour. That is why A and P codes read so differently even though both describe certified equipment.
Certification is the other distinction the letter encodes. A certified unit — the A container or the P pallet — is approved as part of the aircraft's load-restraint system, so it can be locked into position and relied on to hold cargo through the loads of flight. A non-certified, forkable container such as a D unit stows and moves cargo but is not itself part of that restraint system. The difference matters to the people planning the load, which is why it lives in the very first character of the code rather than in a separate field. Reading the letter, then, is not trivia: it is the fastest way to know whether a unit can go where the plan says it should.
The serial and owner code carry their own weight too. The serial keeps two otherwise-identical units apart, and the owner code — usually the airline's IATA code — says who is responsible for the unit and where it should eventually return. On the paperwork those two parts are what let a specific physical container be matched back to a specific line of data, which is exactly what reconciliation depends on.
Where ULD codes show up on the air waybill
ULD numbers and counts surface in the pieces and loading data on the air waybill and manifest, and they matter for weight and load planning. The unit's identifier ties the cargo to a specific piece of equipment, and its tare and capacity feed the weight figures the carrier plans around. When the numbers on the paperwork match the numbers on the ramp, reconciliation is quick; when they don't, someone has to chase the discrepancy before the load is signed off.
A mistyped ULD number is a classic source of that friction. Transpose two digits in the serial, or read a contour letter wrong, and the identifier no longer reconciles against what was physically loaded — the count is right but the reference is wrong, and the mismatch has to be found and corrected by hand. On a busy build-up that is exactly the kind of avoidable delay that eats into a tight departure.
Why reading them right matters for capture
The ULD code packs type, size, and shape into three characters, so reading one wrong misidentifies the equipment — not just a typo, but the wrong container class on the record. That is why capturing ULD identifiers cleanly off the source document is worth doing carefully. AWBGuru captures ULD identifiers from the paperwork as part of its air waybill data extraction, so the type code, serial, and owner come through exactly as printed instead of being re-keyed. It is the same discipline that applies to special handling codes and every other short, meaning-dense field on the document: read it once, read it right, and let the rest of the pipeline rely on it. For the wider picture of what gets pulled off an air waybill, see what AWB data capture is.