ULD types and dimensions

An AKE (LD-3) container measures roughly 1.92 × 1.45 × 1.62 m inside (75.6 × 57.1 × 63.8”) - about 4.3 m³ once the notch at its base is taken off, and 1,516 kg of cargo. A PMC (P6P) pallet has a 3.17 × 2.44 m base (125 × 96”) and builds to 2.44 m (96”) on a Q6 contour, carrying up to 5,000 kg.

Those two units carry most of the world’s air freight, but neither is the box those numbers suggest. A ULD’s corners are cut away to follow the fuselage, and the same pallet is rated differently depending on which position it flies in. The reference table below lists dimensions, capacity and maximum cargo weight for the containers and pallets in most fleets, and the sections before it explain how to read them.

What is a ULD?

A unit load device is the container or pallet that cargo is built onto before it reaches the aircraft. Building a shipment into ULDs on the ground rather than loading loose pieces is what lets a widebody turn around in hours: the ramp handles a handful of units on rollers instead of several hundred cartons by hand.

ULDs split into two categories. Certified units - the ones with an A or P as the first letter of their code - are approved as part of the aircraft’s structure and are locked into the floor by the aircraft’s own restraint system. Non-certified units are ground equipment: they are fine for storage and transfer, but cargo has to be transferred to a certified unit before it flies. When a forwarder builds its own units rather than handing loose cargo to the airline, the shipment moves as BUP - built up by the shipper - and the build quality becomes the forwarder’s problem rather than the handler’s.

How to read a ULD code

The three-letter IATA code is a specification, not a name. The first letter is the category: A for a certified container, P for a certified pallet, D and F for their non-certified equivalents. The second letter is the base footprint - M is the 125 × 96” pallet base, A is 125 × 88”. The third describes the contour and door arrangement, which is what separates two units that share a footprint.

So a PMC is a certified pallet on the 125 × 96” base with one particular contour, and a PAG is the same pallet on the narrower 125 × 88” base. Alongside these, the older ULD type numbers - LD-3, LD-9, LD-26 - are still what most people say out loud. They map onto the codes: an LD-3 is an AKE, an LD-9 is an AAP.

Contour codes and build height

A pallet has no roof, so its height limit comes from the contour code it is built to, and that code is what the table below shows as height:

• LD - 64”, the ceiling in a lower hold
• Q6 - 96”, the common main-deck build
• Q7 - 118”, full main-deck height on a 747F, 777F or A380F

Q4 and Q5 sit between them for specific freighter positions. The code also fixes the shape of the top: a Q7 pallet loaded in the nose of a 747F has to slope in to clear the crown, which is why the equipment library carries several PMCs that share dimensions but not contours.

The four limits that decide a ULD build

The contour

The one that separates air from every other mode. Lower-deck containers are cut away at the bottom corner to sit against the curve of the fuselage; main-deck builds taper at the top to clear the crown. Flat-floor arithmetic - base area × height - quietly overbuilds both, and the overbuild is discovered at build-up, when the unit will not close, or at the ramp, when it will not go on.

The capacity column in the table below has each container’s contour deducted, which costs between 3% and 15% of the envelope depending on how much of the corner goes - an AKE loses 4%, the A2N’s sloped top 15%. The pallets are the other way round: their base entries are square-topped, and the taper comes with the position they are booked on rather than with the pallet itself.

Maximum gross weight

The published limit is the weight of the loaded unit, so the ULD’s own tare comes out of it before any cargo goes on. A PMC’s tare is around 120 kg and an AAF’s around 250 kg. The payload figures in the table are net of tare - the cargo weight you actually have to work with.

The net edge

Cargo securing nets attach at the edge of a pallet’s base, so the bottom of the build has to stay inside the attachment points while everything above them can use the full width. Raising the load on empty pallets or dunnage buys back that space, and it is worth more often than people expect. Cargo-Planner’s automatic bottom spacer tests whether raising a build improves utilisation and adds the dunnage to the plan when it does.

The position it flies in

The same unit is not the same unit everywhere. A PAG is rated for 5,000 kg in most positions and 2,268 kg in the A1 position of a 767-300F, with a different contour to match. Planning at unit level and discovering the position’s limits at load control is how a build that was accepted on paper becomes an offload.

Why build-up plans fail late

Air freight fails late by design. A container that is 3% overloaded on a vessel is found at the terminal; a ULD that will not fit its position is found on the ramp, after the build, with a departure slot running out. The fix is not a better spreadsheet - it is planning against the real contour and the real position limit at the point where the build is decided, rather than confirming afterwards that it was wrong.

Cargo-Planner builds ULDs against their actual contours, keeps each unit inside the weight limit of the position it is booked on, and can load whole aircraft from the same cargo list - so what leaves the build-up area is what the load plan said would fly. The table below has the numbers to plan against, and the calculator underneath turns them into an answer for your own cargo.