What is a ULD and why does it matter for air freight?

A ULD (Unit Load Device) is a container or pallet designed to be loaded with cargo and then loaded as a single unit into an aircraft hold. ULDs serve two purposes: they allow cargo to be pre-loaded on the ground before the aircraft arrives — reducing aircraft ground time — and they distribute cargo weight across the aircraft floor in a certified, predictable way. Without ULDs, cargo would need to be loaded piece by piece into the aircraft hold, which is slow, inefficient, and difficult to control for weight and balance purposes. The standardisation of ULD types and dimensions allows the same containers to be used across different airlines and aircraft types, enabling the global air freight network.

What is the difference between LD3, LD7, and PMC?

LD3 (IATA code AKE) is the most widely used ULD — a half-width container with an angled front face designed to fit the under-floor hold of wide-body aircraft. It holds approximately 4.5 m³ and up to 1,588 kg. LD7 (AKH) is a full-width container used in B747 and A380 main deck positions, holding approximately 8 m³ and up to 3,175 kg. PMC (Pallet Multiple Contour, code P6P) is an aluminium flat pallet with a net rather than a rigid shell, used mainly on B747 main deck; it holds up to 6,804 kg and can accommodate irregular cargo shapes that would not fit in a rigid container. The choice between these types depends on the aircraft operating the route, the dimensions of your cargo, and the airline's ULD policy.

How heavy can a ULD be when fully loaded?

The maximum gross weight (MGW) of a loaded ULD is certified per ULD type: LD3 (AKE) = 1,588 kg; LD6 (ALF) = 3,175 kg; LD7 (AKH) = 3,175 kg; LD11 (AMP) = 6,804 kg; PMC (P6P) = 6,804 kg. These are the IATA-certified limits. Individual airlines may apply lower operational limits for specific aircraft or routes. The MGW includes the tare weight of the ULD itself — for an LD3 container, the tare is approximately 90–110 kg, meaning the actual cargo capacity is slightly below the MGW. The airline will weigh the loaded ULD before loading onto the aircraft — if it exceeds the MGW, cargo must be removed.

Can dangerous goods be loaded in a ULD?

Yes, with additional requirements. All dangerous goods in ULDs must comply with IATA DGR (Dangerous Goods Regulations). The DGD (Dangerous Goods Declaration) must be completed by the shipper, attached to the AWB, and a copy physically affixed to the ULD. Dangerous goods labels (class diamonds) must be applied to the outer surface of the ULD. Some dangerous goods have quantity restrictions per ULD or per aircraft. Class 7 (radioactive materials) has specific stowage restrictions — minimum separation distances from crew and passengers. Certain goods are forbidden in passenger aircraft holds and may only be carried on all-cargo aircraft (Cargo Aircraft Only — CAO). Never mix incompatible dangerous goods classes in the same ULD.

What is the difference between a ULD and bulk loading?

Bulk loading means cargo is loaded individually into the aircraft hold without a container or pallet — each piece is placed by hand into the hold. Bulk loading is used in the lower deck of narrow-body aircraft (B737, A320, A321) where the hold height does not permit ULDs. It is slower, more labour-intensive, and limits individual piece weight to 32 kg (or up to 80 kg with special handling in some cases). ULD loading is faster (a forklift or cargo loader places a pre-built ULD as a single unit), allows heavier individual pieces, and provides better protection for cargo. Most wide-body aircraft use ULDs for lower deck cargo. The main deck of freighter aircraft (B747F, B777F) uses large main-deck pallets and containers. For high-value, time-sensitive, or fragile cargo, ULD loading is always preferred over bulk.

Air Freight Guide

Air Freight ULD Guide

A unit load device transforms loose cargo into a single structural unit that fits precisely into an aircraft hold. Get the build-up wrong and the ULD fails the load acceptance check — or worse, shifts in flight.

Standard ULD types

LD3, LD7, PMC

Max LD3 weight

1,588 kg

Governing standard

IATA ULD Regulations

Floor load limit

~730 kg/m²

ULD Type Comparison

Select a ULD type to see dimensions, capacity, and compatible aircraft

AKE

LD3 Container (AKE)

Internal length

1,534 mm

Internal width

1,534 mm

Internal height

1,630 mm

Max gross weight

1,588 kg

Approx. volume

~4.5 m³

Compatible aircraft

B737, B767, B777, A330, A350

Air Cargo Guide

How to build up and deliver a ULD

A correctly built ULD is structurally sound, within weight limits, within the aircraft contour, properly netted, and fully documented. Every one of these must be true — not most of them.

Step 1

Select the right ULD type for your cargo and route

ULD selection depends on the cargo dimensions, weight, and the aircraft type operating the route. LD3 containers (AKE) are the most versatile — they fit in the lower hold of most wide-body aircraft (B767, B777, A330, A350) and the main deck of narrow-body freighters. LD7 containers or PMC pallets are used on B747 and A380 main deck positions. For unusual cargo shapes (machinery, artwork, vehicles), a PMC pallet with a net allows more flexible build-up than a rigid container. Bulk loading applies only to unpressurised lower holds on narrow-body aircraft (B737, A320) and is limited to 32 kg per individual piece. Confirm the ULD type with the airline or ground handling agent — each aircraft position has a certified ULD type.

Step 2

Check the ULD condition before build-up

Before loading any cargo, inspect the ULD for damage. IATA ULD Regulations specify that a ULD with any structural damage — bent or cracked frame, damaged flooring, holes in the shell — must not be used. Damaged ULDs must be tagged and removed from service for repair by an approved ULD maintenance facility. For containers: check the door seal, hinges, and latches. For pallets: check the pallet base for warping, cracks, and that all tie-down rings are present and undamaged. Record the ULD tag number (ULD identification plate showing ULD type, serial number, and maximum gross weight) and verify the maximum gross weight before building the load.

Step 3

Build the ULD — heaviest items at base, CoG within footprint

Build the ULD on a ULD dolly or build-up stand to allow forklift access. Start with the heaviest items on the base layer, centred over the ULD footprint. The combined CoG of the loaded ULD must be as close to the geometric centre as possible — off-centre loads create asymmetric loading on the aircraft floor rails. Stack progressively lighter items on top. For containers, cargo must remain within the container walls — nothing can protrude. For PMC pallets, cargo must remain within the published aircraft contour for the specific aircraft type (each airline provides a contour template for each pallet position). Exceeding the contour will result in the ULD being rejected at the aircraft door.

Step 4

Apply the cargo net and verify tie-down points

For PMC pallets and some open-sided containers, a cargo net is required to contain the load. The net must be rated for the weight of the cargo — never use a net with a lower rated load than the cargo weight. Attach the net at all designated anchor points around the pallet edge. The net must be taut — slack netting allows cargo to shift. For closed containers, the door or panel must be fully latched. After netting, inspect the build: no cargo protrudes beyond the contour, the net has no visible damage, all anchor points are engaged, and the weight is within the ULD maximum gross weight. Heavy items must be individually secured within the ULD — they must not rely solely on the cargo net.

Step 5

Tag the ULD and complete the Air Waybill (AWB)

Every ULD must carry a ULD tag specifying: the ULD number, destination airport (IATA 3-letter code), shipper and consignee reference, and gross weight of the loaded ULD. The Air Waybill must record: the ULD type code, ULD serial number, gross weight including tare, and the piece count of cargo inside. For dangerous goods in the ULD, the DGD (Dangerous Goods Declaration) must be attached to the AWB and a dangerous goods sticker must be affixed to the ULD itself. The airline checks ULD weight using ramp scales — if the actual gross weight exceeds the certified maximum, the ULD cannot be loaded. Accuracy of declared weight is a safety requirement, not just a billing matter.

Step 6

Deliver to the cargo facility within the cut-off time

Each airline and airport has a cargo cut-off time — the latest time a shipment can be accepted for a specific flight. For ULDs built up by the shipper or freight forwarder, the cut-off is typically 3–4 hours before aircraft departure. ULDs accepted after the cut-off will be held for the next available flight. On arrival at the cargo facility, the ULD is weighed and inspected by the ground handler. If the ULD fails the weight check, contour check, or documentation check, it will be off-loaded and rebuilt — which can take hours. Invest time in building and checking the ULD correctly to avoid holds and rebook costs.

ULD Regulations

ULD rules at a glance

Based on IATA ULD Regulations (ULD-BR), IATA Dangerous Goods Regulations (DGR), and aircraft type-specific contour constraints. Always verify requirements with the operating airline.

Max LD3 gross weight

1,588 kg

AKE — most common type

Max PMC gross weight

6,804 kg

P6P — B747 main deck

IATA ULD Regulations

IATA ULD-BR

Governing standard

Aircraft contour

Must not exceed

Per aircraft type and position

ULD weight limits

Certified per ULD type

Every ULD has a certified maximum gross weight (MGW) marked on its identification plate. This is not a guideline — it is a structural limit certified by the ULD manufacturer and accepted by the airline. Exceeding the MGW compromises the structural integrity of the ULD, the aircraft floor attachment points, and the weight and balance calculation for the flight. Common ULD weight limits: LD3 (AKE) = 1,588 kg; LD7 (AKH) = 3,175 kg; PMC (P6P) = 6,804 kg; LD11 (AMP) = 6,804 kg. Individual airlines may set lower operational limits than the certified MGW — check the airline's specific ULD manual.

Aircraft contour constraint

Build within contour — no exceptions

Each ULD position in an aircraft has a specific contour — a cross-sectional shape that the loaded ULD must fit within, determined by the aircraft fuselage geometry. For PMC pallets, the contour varies between aircraft types and even between positions on the same aircraft. An LD3 container is pre-shaped to fit the under-floor hold contour of wide-body aircraft. A loaded ULD that exceeds the contour will be rejected at the aircraft door — the aircraft door literally will not close around it. Contour templates are available from the airline or ground handler. For irregularly shaped cargo on PMC pallets, physically check the contour with the template before netting.

Dangerous goods in ULDs

Additional rules and labelling

Dangerous goods in ULDs are governed by IATA DGR (Dangerous Goods Regulations). Key rules: the DGD must be attached to the AWB before the ULD is accepted; a Class label and Cargo Aircraft Only (CAO) label must be affixed to the ULD if applicable; radioactive materials (Class 7) have specific ULD position restrictions on the aircraft; certain dangerous goods are prohibited in passenger aircraft holds (Forbidden on Passenger Aircraft — FPA) and may only travel on all-cargo aircraft. Never mix incompatible dangerous goods in the same ULD — IATA DGR Table 9.3 specifies which goods cannot be co-loaded.

Frequently Asked Questions

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