Air Cargo Pallets and ULDs: PMC, PAG Codes, Sizes and Limits

Air cargo pallets are flat aluminium unit load devices (ULDs) that lock into an aircraft's cargo system; the two workhorses are the PMC at 317.5 × 243.8 cm (125 × 96 in) and the PAG/PAJ at 317.5 × 223.5 cm (125 × 88 in). Shippers' wooden or plastic pallets are not loaded into aircraft on their own but are built up on these ULDs, netted and strapped, within contour heights and weight limits set by the airline and aircraft.

What a ULD is

A unit load device is a pallet or container that interfaces directly with the aircraft's floor rollers and restraint locks. Because it becomes part of the aircraft's restraint system in flight, a ULD is treated as aircraft equipment: certified types must meet airworthiness requirements, and their construction, marking, handling and repair are covered by the IATA ULD Regulations (ULDR), the industry's reference manual.

ULDs fall into two families:

• Pallets: a flat aluminium plate with an edge rail that has seat-track fittings for nets and straps. The cargo is held down by a certified net.
• Containers: enclosed units such as the lower-deck LD3 (code AKE), which do not need a net.

Air cargo pallets have nothing to do with the wooden pallets used on the ground, except that ground pallets often travel on top of them. IATA estimates that repair and loss of ULDs cost the industry about USD 400 million a year, which is why airlines are strict about how ULDs are built up and handled.

Reading the ULD identification code

Every ULD carries a 10-character code under IATA Resolution 686, for example PMC 12345 LX.

The first three letters therefore describe the physical unit. Several codes share the same base dimensions, so forwarders often group them: PAG, PAJ and related codes on the 88 × 125 in base are listed as P1P pallets, and the PMC family on the 96 × 125 in base as P6P.

Common air cargo pallets and their limits

Figures are typical carrier values; each airline publishes its own limits for each aircraft type, and the airline's figures always govern. Maximum gross weight includes the ULD, net and cargo.

PHOTO 1An aluminium PMC air cargo pallet built up with boxed cargo, covered by a cargo net on a roller bed at an airport cargo terminalassets/img/rehber/air-cargo-pallets-ulds-1.jpg

Contour heights

A built-up pallet must fit the curved shape of the fuselage. Airlines define contours, and the third code letter or the build sheet tells handlers which one applies.

On a lower deck PMC the usable volume is around 11.5 m³, on a 96 in main-deck build about 17 m³ and on a 118 in build about 21 m³. The top corners of main-deck contours are chamfered to follow the fuselage, so tall, square loads may not use the full height at the pallet edges. Height always includes the pallet base, any wooden pallets, the net and the straps.

Building wooden pallets onto ULDs

Most air freight leaves the shipper on conventional pallets. The handling agent then places these onto the ULD and secures them. Shippers who understand the build-up rules can avoid rejected or re-worked loads.

Footprint and orientation

The usable build area inside the edge rail is smaller than the nominal base; one European carrier quotes about 304 × 230 cm for a PMC. Ground pallets such as the Euro pallet (120 × 80 cm) therefore rarely tile the surface perfectly, and handlers mix orientations and fill gaps with smaller pieces. Pallets should not overhang the ULD unless the airline allows it for that aircraft. Where it is allowed, carriers usually require the cargo to be raised so it clears the ULD edge.

Weight spreading

Aircraft floors and ULD bases have load limits. Heavy, concentrated items need shoring, meaning timber boards or skids placed under the load to spread the weight. One major US carrier's shipper guidelines say shoring may become necessary for concentrated loads over about 1,000 kg (2,200 lb) and recommend double-faced wooden pallets because they spread weight better than single-deck pallets. Shoring also stops the aluminium base from bowing when nets and straps are tightened.

Restraint

The net is the primary restraint, and straps are secondary. Straps are attached to the seat track in the pallet rail. Stretch film alone does not restrain cargo in flight, although stretch wrapping keeps cartons together on the ground pallet.

Weight of the ground pallet

Every kilogram counts in air freight. A wooden Euro pallet weighs around 25 kg, which is why many air shippers use lighter corrugated or paper pallets or nestable plastic pallets for one-way shipments. See the pallet weight guide for typical figures.

PHOTO 2Handlers placing a shrink-wrapped wooden pallet onto timber shoring boards on a PAG pallet before nettingassets/img/rehber/air-cargo-pallets-ulds-2.jpg

Chargeable weight and phytosanitary rules

Air freight is charged on the greater of actual weight and volumetric weight. Under the IATA convention, 6,000 cm³ count as 1 kg, so a 1.2 × 0.8 × 1.5 m pallet load (1.44 m³) has a volumetric weight of 240 kg. A light but bulky load on a heavy wooden pallet is therefore charged by volume, while a dense load is charged by gross weight including the pallet.

Wooden pallets in air freight are still international wood packaging. Most importing countries apply ISPM 15 to solid wood pallets regardless of transport mode, so export pallets must be treated and marked. Processed wood, plastic, metal and paper pallets fall outside ISPM 15.

Frequently asked questions

Sources

1. ULD Regulations (ULDR) — IATA
2. ULD Identification Codes Demystified — ULD CARE
3. P6P/PMC Pallet — DSV
4. P1P/PAG Pallet — DSV
5. ULD Specifications — AirBridgeCargo Airlines
6. Shipper Built ULD Guidelines — United Cargo
7. Calculation of Air Freight (trainer slides) — ASEAN