Air Freight ULDs Explained: Pallets, Containers, Pivot Weight and Contour

When you book air freight from China, the rate you are quoted is shaped by something most importers never see: the unit load device, or ULD. These are the aluminium pallets and containers that cargo is built onto before it goes into the aircraft belly or main deck. Understanding how ULDs work explains why air freight has a “pivot weight,” why odd-shaped cargo pays more, and why your carton dimensions matter as much as their weight.

What a ULD is

A ULD is either a pallet with a net, or an enclosed container, built to fit the curved cross-section of a specific aircraft type. Cargo is stacked and shrink-wrapped onto the pallet or loaded into the container at the airline’s build-up area, the whole unit is weighed, and it is then loaded as one piece by the aircraft’s cargo loading system. Your individual cartons are consolidated with other shippers’ cargo onto these units. The airline is not really selling you space by the carton; it is selling you a share of a ULD and, above that, a share of the aircraft’s weight and volume limits.

Chargeable weight and the density problem

Air freight is billed on chargeable weight: the greater of actual weight and volumetric weight. Volumetric weight converts the space your cargo occupies into a weight figure using a standard divisor. Light, bulky cargo — think inflatable goods, empty plastic housewares, foam — is charged on volume because it fills a ULD long before it reaches the weight limit. Dense cargo — hardware, tools, printed matter — is charged on actual weight. This is covered in full in air freight chargeable weight explained; the ULD is the physical reason the rule exists.

Pivot weight and ULD rates

For full-ULD shipments, airlines often use a pivot system: a ULD has a pivot weight included in a flat ULD rate, and weight above the pivot is charged at an over-pivot rate per kilo. If your cargo comes in under the pivot, you have effectively paid for weight you did not use; if it goes well over, the marginal kilos are cheaper than the base rate. This is why a forwarder consolidating many shippers onto one ULD can sometimes beat a small shipper’s loose rate — they are buying at the ULD level and filling it efficiently. For most Bangladeshi importers shipping a few hundred kilos, you are on loose general cargo rates and the pivot is the forwarder’s concern, but it explains the pricing behaviour you see.

Contour: why shape matters

A ULD has to fit the aircraft, so cargo built onto a pallet cannot be a simple rectangular block — the top edges must be cut back to follow the fuselage curve, called the contour. Cargo that cannot be stacked or nested to that shape wastes ULD volume, and wasted volume is wasted money. Cartons of uniform size that stack into a stable, contourable block are the cheapest to fly. Long items, tall rigid items, and a jumble of mixed carton sizes all reduce how much usable cargo fits on a pallet, which the forwarder recovers in the rate or a handling surcharge.

Belly hold vs main deck

Passenger aircraft carry cargo in the belly hold on smaller ULDs; freighters carry larger ULDs on the main deck as well. From China to Bangladesh, a lot of capacity is belly hold on passenger services, which limits the size of any single piece — anything too tall or too long for a belly ULD needs a freighter and is priced and scheduled differently. If you have one large item, tell the forwarder its exact dimensions early so they route it correctly rather than discovering at build-up that it will not fit the planned aircraft.

What this means for how you pack

• Use uniform carton sizes that stack into a stable block — mixed sizes waste ULD space you pay for.
• Keep individual cartons within belly-hold height and length unless you have confirmed freighter capacity.
• Calculate volumetric weight before you book so the chargeable weight is not a surprise on the invoice.
• For light bulky goods, consider whether sea freight or LCL is the better mode — you are paying for air by volume anyway.
• Palletise and strap at origin if the forwarder allows it, so your cargo is not restacked loose.
• Give the forwarder accurate dimensions and weights — a re-weigh and re-measure at the airport that exceeds your declared figures leads to a rate correction.

ULD damage and the odd charge you might see

ULDs are airline equipment with real value, and their movement is tracked. You will not normally be billed for ULD handling as a line item on a small consolidation, but on full-ULD bookings you may see references to ULD control, demurrage on units not returned, or build-up and break-down fees. If one appears on your invoice, ask the forwarder to explain which unit and why. Our guide to what affects air freight pricing lists the surcharges that legitimately appear.

Loose-loaded (bulk) cargo versus ULD build

Not all air cargo goes onto a ULD. Smaller aircraft and some narrow-body services are bulk-loaded — individual pieces handed into the hold and stacked by hand. Bulk loading puts a real limit on piece size and weight, because a loader has to lift and manoeuvre each carton through a small hatch. If your cargo has any large or heavy single pieces, tell the forwarder early so it is routed onto a service that can ULD-build it; finding out at the airport that a piece cannot be bulk-loaded means a delay to the next suitable flight. For uniform, hand-sized cartons, bulk loading is fine and common on the shorter China–Bangladesh sectors.

Temperature, and ULDs for sensitive cargo

An aircraft hold is not a controlled environment the way a reefer container is. Temperature-sensitive air cargo — pharma, some foods, certain electronics — either travels in an active temperature-controlled ULD, which is booked specially and costs a premium, or relies on passive insulated packaging and thermal blankets over a standard build. If your goods have a temperature limit, state it at booking and agree in writing how it will be protected, rather than assuming the belly hold will be cool enough. Our guide on perishable cargo by air covers the packaging options.

What to give the forwarder at booking

• Exact dimensions and gross weight of every carton type, and the piece count — not estimates.
• The largest single piece’s dimensions and weight, called out separately.
• Whether cartons are palletised at origin or handed over loose.
• Any temperature, orientation (this way up), or dangerous-goods characteristics.
• Your target flight or latest acceptable arrival, so they can plan the build and the routing.
• Declared value for carriage and whether you want cargo insurance arranged.

Shipping by air from China and want the rate to make sense? Send us your carton dimensions, weights and piece count and we will tell you the chargeable weight, whether your cargo palletises efficiently, and whether air or sea is the right mode for the value and urgency. See our services, reach us on the contact page, use our China sourcing and buying agent service, or browse the shop.