Air cargo doesn't load loose. Nearly everything that flies in a widebody's belly or on a freighter's main deck travels on a unit load device — a ULD — either an aluminum pallet with a cargo net or a closed container shaped to the aircraft's fuselage. The sizes are standardized under IATA's ULD Regulations, which is why a forwarder in Seoul and a handler in Frankfurt can talk about a "PMC" and mean exactly the same footprint. This guide lists the dimensions that matter, explains the height and contour limits that trip people up, and covers how BUP pricing turns ULD geometry into money.
Air freight pallets
An air freight pallet is a flat aluminum sheet with seat tracks around the rim; cargo is stacked on it, wrapped, and secured under a rated net. Unlike a wooden warehouse pallet, the pallet itself is aircraft equipment, registered to an airline and returned after the flight.
| Type | Base (in) | Base (cm) | Typical max gross | Common use |
|---|---|---|---|---|
| PMC / P6P | 96 × 125 | 244 × 318 | ≈6,800 kg | The workhorse — widebody lower deck and freighter main deck |
| PAG / P1P | 88 × 125 | 224 × 318 | ≈6,000 kg | Older standard, still common on many aircraft |
| PLA | 60.4 × 125 | 153 × 318 | ≈3,000 kg | Half pallet for smaller consolidations |
| PGA | 96 × 238.5 | 244 × 606 | ≈11,300 kg | 20-ft pallet for freighter main decks, outsize pieces |
Weight limits are nominal maxima — the allowable gross for a given flight depends on the aircraft type and the position the ULD occupies, so treat the airline's booking confirmation, not the table, as final.
Air freight containers
Containers (airlines say "cans") are closed boxes, most with one angled or cut-away side so they nest against the curved fuselage — the contour. That angle is why an air container's usable volume is smaller than its rectangular bounding box suggests.
| Type | Base (cm) | Height (cm) | Volume | Typical max gross | Fits |
|---|---|---|---|---|---|
| AKE (LD3) | 156 × 153 | 163 | ≈4.3 m³ | ≈1,588 kg | Every widebody lower deck — the default belly can |
| AKH (LD3-45) | 156 × 153 | 114 | ≈3.5 m³ | ≈1,134 kg | A320-family lower deck |
| AAP (LD9) | 318 × 224 | 163 | ≈10.5 m³ | ≈4,600 kg | PAG-footprint container, widebody lower deck |
| AMA | 318 × 244 | 244 | ≈17 m³ | ≈6,800 kg | Main-deck container for freighters |
Height limits: the same pallet, three ceilings
The base sizes above are fixed; the buildable height is not. It depends on where in the aircraft the ULD rides:
Lower deck (belly): about 160–163 cm (64 in) of build height on a PMC or PAG, with the top edges chamfered to the hold's curve. This is the limit that governs most general cargo on passenger flights.
Main deck, standard freighter positions: about 244 cm (96 in), with a contoured shoulder on positions against the fuselage wall.
Main deck, tall positions (e.g. 747F center positions): up to roughly 300 cm (118 in) — the numbers behind "a 747 can swallow a small truck".
Practical consequence: a shipment 170 cm tall cannot ride a passenger aircraft's belly at all, no matter how light it is. If your cargo is between about 160 and 300 cm tall, the available aircraft — not the price — decides your routing, so tell your forwarder the height before anything else.
BUP: when the forwarder builds the ULD
Airlines normally build ULDs themselves at the terminal. Under a Bulk Unitization Programme (BUP), the airline instead hands empty ULDs to a forwarder, who builds them at its own warehouse and tenders them back ready to fly — sealed, contour-checked, netted. The shipper-built unit skips the airline's build-up queue, which typically means later cut-offs, faster recovery at destination, and fewer handling touches on the freight.
The commercial engine is the pivot weight. BUP rates are commonly structured per ULD: a flat rate that covers the unit up to an agreed pivot (for a PMC, often in the 4,000–5,000 kg range), plus a per-kg charge above it. The forwarder, meanwhile, charges each customer by chargeable weight. The difference between what a well-packed pallet earns and what it costs is consolidation margin — which is why forwarders care intensely about building tight, tall-as-allowed, contour-perfect pallets.
Planning cargo onto a ULD footprint
For a first-order fit check, treat the ULD as a box: PMC base 318 × 244 cm at 160 cm build height in the belly gives roughly 10.8 m³ of envelope, before the chamfered top corners shave a little off. Cartons that tile the base efficiently matter more than clever stacking — a 318 cm side divides cleanly by 53, 63.5, 79.5 cm cartons, and dead strips along the rim are pure lost revenue on a per-ULD rate. Weigh the build as you go: hitting the volume ceiling and the pivot weight at the same time is the packing optimum, and the CBM calculator gives you the density target to aim for.
Reading ULD type codes
Every ULD ID follows the same IATA pattern — three letters, serial number, owner code, e.g. PMC 45231 KE. The first letter is the category (P = pallet, A = certified container), the second encodes the base size (M = 96×125 in, A = 88×125 in, K = LD3 base), and the third the contour or compatibility variant. You rarely need the full decoder table: recognizing PMC, PAG, PLA, AKE and AKH covers the overwhelming majority of airway bills.