Air Cargo Container (ULD) Sizes

A ULD is any device that lets loose cargo load as one unit into an aircraft’s cargo system. The hold floors carry powered rollers and locks that grip the ULD’s base, so a unit of up to 1.6 tonnes moves with a fingertip and stays put in flight. Two families exist:

The split is practical, not cosmetic. Containers protect cargo, load fast, and dominate lower-deck (belly) freight on passenger aircraft. Pallets take awkward and oversized pieces a can will not swallow, and dominate freighter main decks, where cargo can be stacked to 244 or even 300 cm under the crown of the fuselage.

Both are certified aircraft equipment: a ULD is legally part of the aircraft, built to airworthiness standards, weighed and inspected. That is why a battered can gets pulled from service the way a cracked wheel would.

Every row is what the ULD sheets print: Boeing’s of 2012 and the ULD pages of Air Canada Cargo, IAG Cargo, Vietnam Airlines Cargo and AirBridgeCargo, read on 18 October 2026.

Where they print different figures — a tare that depends on the door, a volume, a rating that depends on the aircraft — the table gives their range. The AMA row rests on Boeing’s sheet, which AirBridgeCargo’s page repeats, and an aircraft position may allow less than a unit’s rating.

Three of these carry most of the world’s belly freight:

The AKH (LD3-45) is the special case — an LD3 footprint squashed to 114 cm so it fits the shallow holds of the A320/A321 family, the only narrow-body line with containerised cargo. At the top end, the AMA (M1) is a full-height main-deck box, roughly 4 LD3s’ capacity in one unit.

Note how light the hardware is. An LD3 tares at 62–82 kg against a 20 ft sea container’s 2,230 kg (its sheets print 2,080–2,570 kg): aluminium versus Corten steel. Every kilogram of tare is a kilogram of revenue payload burned in fuel. It is also why ULDs dent so easily, and why ground crews treat them (in theory) like aircraft parts rather than boxes.

An LD3 container measures 156 × 153 × 163 cm (61.5 × 60.4 × 64 in) externally, as 4 independent documents print it (Air Canada Cargo, Boeing Commercial Airplanes, IAG Cargo and Vietnam Airlines Cargo). It holds 4.2–4.5 m³ depending on the sheet and is certified to 1,588 kg maximum gross, as 3 independent documents print it (Air Canada Cargo, Boeing Commercial Airplanes and Vietnam Airlines Cargo), at a tare of 62–82 kg.

Its door opening is 140–147 × 150–155 cm depending on the sheet. It is the same unit the spec table above lists under its IATA code AKE. One base corner is cut away at an angle so the can nests against the lower-fuselage curve, which is what makes the LD3 a belly container rather than a simple box.

Those numbers make it the default cell of air freight planning: quotes for wide-body belly capacity are effectively quotes in LD3 positions, at roughly 1.5 tonnes of cargo and 4.2–4.5 m³ per position. Cargo that exceeds 163 cm of height, or a single piece heavier than the gross rating, leaves the LD3 world entirely and needs a pallet position instead.

An LD7 is the traditional name for the netted 125 × 88 in pallet load: a PAG-coded aluminium pallet with a 318 × 224 cm base. It builds to 10.5–11.9 m³ under the net at a maximum gross of 4,600–6,800 kg, depending on the sheet and the aircraft position. The name predates the IATA letter codes, so quotes may say LD7, PAG or P1P for what is physically the same lower-deck pallet position.

The PMC is its wider sibling — 125 × 96 in (318 × 244 cm), rated to 5,098–6,800 kg (5,098 kg on Air Canada Cargo’s sheet, 6,800 kg on Vietnam Airlines Cargo’s). It holds 11.5–12.7 m³ when built to the 163 cm belly contour, and has largely displaced the 88-inch base as the workhorse pallet of the fleet.

On a freighter main deck the same PMC base builds far higher. Boeing’s sheet, which AirBridgeCargo’s page repeats, gives 17.0 m³ at 244 cm and 21.2 m³ at 300 cm.

Compatibility is fixed by hold cross-section.

Freighter main decks: B747F, B777F and A350F carry PMC pallets contoured to about 3.0 m tall and M1 containers on the main deck, with standard LD3/PMC positions below. The practical consequence for shippers: belly capacity on a passenger wide-body prices and books like a fleet of 1.5-tonne cells, while a freighter sells pallet positions rated up to 6.8 tonnes. Cargo taller than 163 cm cannot fly in a belly can at all.

Temperature-controlled air freight — pharmaceuticals above all — moves in powered or passive cool containers whose codes start with R. The RKN is a reefer on the LD3’s 156 × 153 cm base (door 137 × 140 cm on AirBridgeCargo’s sheet). The RAP is one on the LD9’s 318 × 224 cm base; the sheets read rate them 1,588 kg and 4,626–6,033 kg gross.

Active units (Envirotainer, va-Q-tec and CSafe lease them) hold a set temperature on battery power with compressor or dry-ice cooling. They do so for a number of hours each lessor states by model and outside temperature — the margin that matters on the tarmac, where most cold-chain excursions actually happen.

They rent by the trip at rates that dwarf the freight itself, and they weigh. An RKN tares 210 kg on Boeing’s sheet and 630–670 kg as an active unit on Air Canada Cargo’s, against 62–82 kg for a plain AKE, all of it deducted from payload. The economics only close for cargo where an excursion costs more than the container — which describes vaccines and biologics exactly.

An LD3 holds 4.2–4.5 m³ — about 13–14% of a 20 ft sea container’s 33.2 m³. Repacking a full 20 ft box for the air leg therefore takes 7–8 LD3s by volume (7.4–7.9 units by the sheets’ volumes, before the packing losses of the LD3’s angled corner).

Ocean and air capacity are quoted in units that never meet on one page, so here is the bridge for the larger boxes:

Weight tells the sharper story. The 20 ft box carries 28,250 kg of payload. 7–8 LD3s, at 1,506–1,526 kg of cargo each (gross rating less tare), carry 10.5–12.2 tonnes between them.

Sea freight fills volume and weight together; air freight runs out of weight allowance long before space when cargo is dense. That is why sea-to-air repacks split one container across many flights, and why the mode switch is priced per kilogram, never per box.

To run your own cargo through both systems, start from its volume in the CBM calculator and the per-container capacities in the container CBM guide.

Every ULD wears a code like AKE 12345 LH: three letters, a serial number, and the owner’s airline code. The letters decode mechanically:

So AKE = certified container, LD3 base, belly contour; PMC = certified pallet, 125 × 96 in, contour C; RKN = reefer on the LD3 base. The system is the air-side sibling of the ISO 6346 codes on sea container doors, decoded in our ISO standards guide — same idea, different alphabet.

Air freight charges the greater of actual weight and volumetric weight at 1:6,000 — volume in cm³ divided by 6,000, i.e. 1 m³ = 167 kg. Sea LCL uses 1:1,000 (1 m³ = 1,000 kg), so almost all ocean cargo is billed by volume, while any cargo lighter than 167 kg per cubic metre is billed volumetrically by air. Both modes protect themselves against light, bulky cargo, but with different divisors.

An LD3 of 4.2–4.5 m³ filled with light goods bills as at least 700–750 kg of chargeable weight regardless of what the scale says.

The full mechanics — DIM factors for sea, air and courier, with worked examples — are in the CBM calculator. The one-line summary: sea sells you a box, air sells you kilograms, and the ULD is just the tray they load them on.