A unit load device (ULD) is a standard aircraft pallet or container that locks into the aircraft's cargo system so freight is loaded as one unit instead of piece by piece. The two most common air cargo pallets are the PMC, with a 96 × 125 in (244 × 318 cm) base, and the PAG, with an 88 × 125 in (224 × 318 cm) base.
Key takeaways
- A ULD is a pallet or container that locks into the aircraft floor; the AKE (LD3), PMC and PAG cover most air cargo.
- PMC pallets are 96 × 125 in (244 × 318 cm) and PAG pallets 88 × 125 in (224 × 318 cm); both can be built to about 64 in (163 cm) in the lower deck.
- On freighter main decks, pallets and containers such as the AMA and AMJ go to 96 in (244 cm), and some positions allow 118 in (300 cm).
- The three-letter ULD code gives the unit type, base size and contour, followed by a serial number and the owner's two-character code.
- Maximum weights differ between owners and aircraft, so confirm the limit for your exact ULD and position with the airline.
What is a ULD?
A unit load device (ULD) is an aircraft pallet or container that locks into the aircraft's cargo system, so many pieces of freight are loaded and secured as one unit. The workhorses are the AKE (LD3) container and two pallets: the PMC at 96 × 125 in (244 × 318 cm) and the PAG at 88 × 125 in (224 × 318 cm).
Instead of loading boxes one by one into the hold, ground handlers build cargo onto ULDs in the warehouse, weigh them, then roll them onto the aircraft where they lock into floor rails. That makes loading faster, protects the cargo and lets the load be balanced precisely. IATA defines a ULD as either an aircraft pallet and net combination or an aircraft container, treats ULDs as removable aircraft parts, and estimates there are about 1 million in service. Its ULD Regulations set the industry standard for how they are specified, built, handled and maintained.
What are the dimensions of each ULD type?
Most ULDs share a handful of base sizes: the LD3 base of 61.5 × 60.4 in, the 125 × 88 in and 125 × 96 in pallet bases, and the long 16-foot and 20-foot freighter pallets. Height and weight then depend on whether the unit flies in the lower deck or on a freighter's main deck.
| IATA code | Common name | Base (in) | Base (cm) | Max height: lower deck / main deck | Max gross weight | Typical aircraft and deck |
|---|---|---|---|---|---|---|
| AKE | LD3 container | 61.5 × 60.4 | 156 × 153 | 64 in (163 cm) / not used | 1,588 kg | Lower deck of wide-bodies: A330, A350, A380, 747, 777, 787 |
| AKH | LD3-45 container | 61.5 × 60.4 | 156 × 153 | 45 in (114 cm) / not used | Up to 1,588 kg (Unilode); some lessors list less, e.g. 1,340 kg | Lower deck of A319, A320, A321 |
| RKN | Active temperature-controlled LD3 | 61.5 × 60.4 | 156 × 153 | 64 in (163 cm) / not used | 1,588 kg | Lower deck; pharma and perishables |
| DPE | LD2 container | 60.4 × 47 | 153 × 119 | 64 in (163 cm) / not used | 1,225 kg | Lower deck, mainly 767 |
| ALF | LD6 container | 125 × 60.4 | 318 × 153 | 64 in (163 cm) / not used | 3,175 kg | Lower deck of wide-bodies |
| AAP | LD9 container | 125 × 88 | 318 × 224 | 64 in (163 cm) / not used | 4,625 to 6,033 kg, varies by unit | Lower deck of wide-bodies |
| AMF | Full-width lower-deck container | 125 × 96 | 318 × 244 | 64 in (163 cm) / not used | 5,000 to 5,100 kg, varies by unit | Lower deck of wide-bodies except the 767 |
| PMC | P6P, "96-inch pallet" | 125 × 96 | 318 × 244 | 64 in (163 cm) / up to 118 in (300 cm) | 5,034 kg belly; 6,804 kg main deck | Lower deck of wide-bodies and freighter main decks |
| PAG | P1P, "88-inch pallet" | 125 × 88 | 318 × 224 | 64 in (163 cm) / up to 118 in (300 cm), varies by position | 4,626 kg belly; 6,804 kg main deck | Lower deck of wide-bodies and freighter main decks |
| PLA | Half pallet | 125 × 60.4 | 318 × 153 | 64 in (163 cm) / varies by aircraft | 3,175 kg | Lower deck of wide-bodies; some freighters |
| PRA / PRF | 16-foot pallet | 196 × 96 | 498 × 244 | Not used / up to 118 in (300 cm) | 11,340 kg standard; up to 23,700 kg with extra restraints (Cargolux) | Freighter main deck |
| PGA / PGF | 20-foot pallet | 238.5 × 96 | 606 × 244 | Not used / up to 118 in (300 cm) | 11,340 to 13,608 kg standard; up to 28,800 kg with extra restraints (Cargolux) | Freighter main deck |
| AMA | M1 main deck container | 125 × 96 | 318 × 244 | Not used / 96 in (244 cm) | 6,804 kg | Main deck of A330F, 747F, 777F, MD-11F |
| AMJ | M1-size main deck container | 125 × 96 | 318 × 244 | Not used / 96 in (244 cm) | 6,804 kg | Main deck of wide-body freighters |
| AMD / AMX | M1H, 118-inch container | 125 × 96 | 318 × 244 | Not used / 118 in (300 cm) | 6,804 kg | Tall main deck positions on 747F and 777F |
Figures come from the published specifications of the freighter airline Cargolux, the ULD manager Unilode, the ULD lessor and manufacturer ACL Airshop and the container maker VRR. Where those sources differ, the table shows the range rather than picking one number. Lower-deck containers such as the LD3 and LD6 are wider at the top than at the base (the LD3 is 79 in, or 201 cm, across the top) because one or both sides slope to follow the fuselage. Exact limits depend on the aircraft type and the position on the deck, so always confirm with the airline before building a heavy unit.
How do you read a ULD code?
Every ULD carries an ID such as AKE 12345 LH: three letters for the unit type, a four- or five-character serial number, and the owner's two-character code.
The format comes from the IATA ULD Regulations and is explained in detail by the industry body ULD CARE:
| Position | Example (AKE 12345 LH) | What it tells you |
|---|---|---|
| 1: category | A | The kind of unit: A is a certified container, P a certified pallet, R a certified thermal (temperature-controlled) container, D a non-certified container |
| 2: base size | K | The base dimensions: K is the LD3 base (61.5 × 60.4 in), A the 125 × 88 in base, M the 125 × 96 in base, L the 125 × 60.4 in base, G the 20-foot 238.5 × 96 in base |
| 3: contour or certification | E | For containers, the IATA contour the unit fits; for pallets, how the pallet is certified and restrained |
| 4 to 8: serial number | 12345 | The owner's unique number for the unit; most use five characters, older units four |
| 9 to 10: owner code | LH | The two-character code assigned by IATA, for airlines normally their designator |
So the second letter tells you the footprint at a glance: an AKE, RKN and AKH all sit on the same LD3 base, while a PMC, AMA and AMJ all use the 125 × 96 in base. Units that look identical can still differ mechanically, so a PAG and a PAJ pallet are not automatically interchangeable; the aircraft's weight and balance manual decides which positions accept which codes. The owner code is always two characters, and writing three can create a different ID in systems that only read two.
What is the difference between a pallet and a container?
A pallet is a flat aluminum base that cargo is stacked on and secured with a net, so it can be shaped to the aircraft's contour; a container is a rigid box with its own walls and door, which protects the cargo but limits what fits inside.
| Pallet (PMC, PAG, PLA, PGA) | Container (AKE, ALF, AMA, AMJ) | |
|---|---|---|
| Structure | Flat base with edge rails, plus a net and sometimes plastic sheeting | Rigid walls, roof and a door or curtain |
| Shape of the load | Built by hand to the contour of the position | Fixed by the container's own shape |
| Best for | Long, heavy, tall or irregular pieces and machinery | Boxed general cargo, parcels, mail, baggage, garments |
| Protection | Depends on the build, sheeting and strapping | Good protection from weather and handling |
| Usable space | The edge rails take some room: Cargolux gives a PAG's usable area as 118.5 × 81.5 in (301 × 207 cm) | Walls take some room: an AMA's interior is about 117 × 90 × 90 in (Cargolux) |
Main deck containers are the large end of the range. The AMA and AMJ sit on the 125 × 96 in base and stand about 96 in (244 cm) tall, so they fit only freighters; VRR lists both at 6,804 kg maximum gross weight. Each holds several times the volume of an LD3 (Unilode gives 17.5 m³ for an AMA against 4.3 m³ for an AKE), which is why integrators and forwarders build them at their own hubs for e-commerce parcels, garments and electronics and fly them as single units. Taller variants such as the AMD and AMX, at 118 in, use the full height of the center positions on large freighters. DSV also lists the AMA as the M1 container.
How tall can cargo be built on the main deck and lower deck?
Lower-deck units on wide-body aircraft are limited to about 64 in (163 cm), and to 45 in (114 cm) on the A320 family, while main-deck freighter positions allow builds of about 96 in (244 cm) and up to 118 in (300 cm) in the tallest positions.
Pallets are built to a contour, a template matching the curve of the fuselage at that position. Lower-deck contours are low and cut away at the corners to follow the belly; the LD3's sloped side is the same idea built into a container. Main deck contours are taller and vary across the aircraft, with the tallest builds in the center positions and lower ones along the sides where the fuselage curves in. Cargolux, for example, lists the same PMC pallet at 64 in for the belly and 118 in for a main deck build.
| Lower deck (belly) | Main deck (freighter) | |
|---|---|---|
| Aircraft | Wide-body passenger aircraft and freighters; narrow-bodies take AKH units | Freighters, plus combi aircraft |
| Typical maximum height | About 64 in (163 cm) on wide-bodies; 45 in (114 cm) on the A320 family | About 96 to 118 in (244 to 300 cm), by position |
| Typical ULDs | AKE (LD3), DPE (LD2), ALF (LD6), RKN, PMC and PAG pallets | PMC and PAG pallets, 16- and 20-foot pallets, AMA, AMJ and AMD containers |
| Typical PMC maximum weight | 5,034 kg (Cargolux) | 6,804 kg (Cargolux) |
| Best for | Mixed general cargo, mail, perishables and pharma on passenger networks | Tall, heavy or high-volume cargo and full-unit bookings |
A pallet built for a freighter's main deck will not fit the belly of a passenger aircraft, which is why tall machinery must fly on freighters. For cargo too long or tall even for a contoured pallet, nose-loading freighters such as the Boeing 747F let long pieces go straight in through the front of the aircraft. That is the space we plan for with JumboPower, and it is often reached through freighters wet-leased by forwarders and airlines, as explained in our guide to ACMI leasing.
How do you build cargo to fit a ULD?
Start from the unit's usable footprint and the contour height of the position it will fly in, then plan piece sizes, stacking and weight so nothing overhangs, breaks the contour or overloads the floor.
- Size cartons to the base. Plan the footprint against the usable area, not the outside dimensions: on a PAG that is about 118.5 × 81.5 in (301 × 207 cm) per Cargolux. Cargo that overhangs the edge rail or breaks the contour may be rejected or rebuilt.
- Respect the floor load. Cargolux lists a bearing limit of 1,465 kg/m² (300 lb/sq ft) for its standard pallets and main deck containers. Heavy concentrated pieces may need spreader boards to spread the load.
- Check the heaviest single piece. A unit can be under its maximum gross weight and still fail on one dense piece, so give the airline the weight and footprint of each heavy item.
- Know which weight you pay for. Light, bulky cargo is charged on volume, so a full unit of low-density freight is billed well above its actual weight. Our air freight cost calculator shows whether actual or volumetric weight applies to your shipment.
- Compare unit rates with per-kilogram rates. Booking a whole ULD at a unit rate can work out cheaper than per-kilogram pricing when you can fill it.
- Book main deck only when you need it. Choosing freighter capacity only for cargo that needs the height avoids paying for space that the belly of a passenger aircraft could have provided.
For example (hypothetical): an AKE holds about 4.3 m³. Filled with light cartons and charged on volume at the common IATA ratio of 6,000 cm³ per kilogram, the chargeable weight would be about 717 kg, even if the cargo itself weighed only 400 kg. For how ULD choice and mode choice affect total cost, see our air freight vs sea freight comparison.
What should you tell your forwarder before a ULD booking?
Give the exact dimensions and weights, how the cargo can be handled, and whether it needs main deck height or a temperature-controlled unit.
- Exact dimensions and weight of every piece, including the heaviest single piece.
- Whether pieces can be stacked, tilted or turned.
- Any lifting points or forklift requirements.
- Temperature or handling needs, which may require an active container such as an RKN.
- Whether you can build the unit at your premises or need it built at the terminal.
- Whether the cargo needs main deck height or can fly in the lower deck of a passenger aircraft.
Frequently asked questions
What is a ULD?
A unit load device (ULD) is an aircraft pallet with its net, or an aircraft container, built to lock into an aircraft's cargo loading system. Freight is built onto ULDs in the warehouse so it can be loaded, secured and balanced as a few large units.
What size is an air cargo pallet?
The two standard sizes are the PMC at 96 × 125 in (244 × 318 cm) and the PAG at 88 × 125 in (224 × 318 cm). Freighters also use 16-foot (196 × 96 in) and 20-foot (238.5 × 96 in) pallets, and a half pallet, the PLA, measures 60.4 × 125 in.
What is a PMC pallet?
A PMC (also P6P) is the 96 × 125 in (244 × 318 cm) aircraft pallet, used in the lower deck of wide-body aircraft and on freighter main decks. Cargolux lists it at 5,034 kg maximum gross weight in the belly and 6,804 kg on the main deck.
What are LD3 dimensions?
An LD3 (IATA code AKE) has a 61.5 × 60.4 in (156 × 153 cm) base, widens to 79 in (201 cm) at the top to follow the fuselage, and stands 64 in (163 cm) tall. It holds about 4.3 m³ and has a maximum gross weight of about 1,588 kg.
What is the difference between PMC and PAG pallets?
Both are 125 in (318 cm) long. The PMC is 96 in (244 cm) wide and the PAG is 88 in (224 cm) wide, and in the lower deck the PMC usually carries a higher maximum weight.
