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All About Air Freight ULDs (Unit Loading Devices)

Updated: May 28, 2023

Everything You Need to Know About Air Freight ULDs (Unit Loading Devices)

Unit loading devices (ULDs) play a critical role in the air cargo industry. They are used to transport many different types of freight, and they're widely available in multiple container and pallet formats.

ULDs offer numerous advantages over other shipping methods, which is why multiple industry sectors have adopted them. They allow shippers to preload cargo, reduce labor costs associated with loading and unloading, and provide industry operators with confidence throughout the transportation cycle.

Air Freight ULDs

Let's take a detailed look at ULDs, from basic categories and specifications to identification standards and industry benefits.

What is a unit loading device (ULD)?

A unit load device or ULD is a special container used to load and transport cargo onto an aircraft. ULDs are constructed in two basic formats. Specialized containers and pallets are both available to transport freight, machinery, luggage, and mail. When the right ULD is selected for the load, freight can be lifted onto a passenger or cargo plane with maximum speed and efficiency.

Depending on their dimensions, ULDs can fit onto wide-body or narrow-body aircraft. They offer a variety of benefits throughout the shipping process, from initial planning and preloading to fitting and final unloading. With the ability to measure aircraft weights and balances effectively and significantly reduced loading times and labor costs, ULDs are the preferred choice for forwarders and shippers throughout the transport industry.

A short history of ULDs

ULDs have a long and successful history in the air transportation sector. They were first introduced in the 1950s to optimize the commercial transportation of cargo. Before they were invented, loading and unloading cargo was a time-consuming and labor-intensive process that caused headaches for many shipping operators.

The first ULDs were basic wooden pallets. While simple, they allowed forklifts to move large quantities of cargo instead of dealing with individual items. Loading and unloading cargo could be performed in a single step, making processes more efficient and reducing bottlenecks. ULDs grew more sophisticated over the years, increasing in complexity to meet the growing needs of the air transportation industry.

Today, ULDs are constructed in container and pallet format. They're made from a variety of materials, and they come in a range of dimensions to accommodate different cargo types. The design and construction of ULDs have come a long way, with advanced materials used to create durable and lightweight shipping units to meet the demands of air travel.

Basic ULD categories

If you're shipping goods across the country or the world, ensuring safe and effective transportation is important. ULDs are available in two broad categories, with both types offering distinct advantages. When selecting a ULD solution, it's important to consider the size, shape, and fragility of your shipment, along with specific details related to loading, unloading, and protection.

The following factors should be taken into consideration:

  • Cargo type and dimensions

  • Loading and unloading requirements

  • Distance from collection to delivery

  • Transit time and urgency

  • Specific cargo requirements

  • Available budget and timeline

ULD receptacles are available in the following two forms:

ULD containers

ULD containers are large receptacles that can be loaded and unloaded between airplanes and warehouses. Containers are generally made of aluminum, and they're often referred to as pods, cans, bins, or PMCs. ULD containers are constructed from a solid and durable material to ensure cargo safety during loading and unloading.

ULD containers offer greater protection than pallets, which makes them popular with large shipments and sensitive materials. They also make loading and unloading faster and help protect against unauthorized access and environmental damage. Cargo placed inside a ULD container doesn't need extra wrapping, and there's no need for corner guards or other protective packaging.

ULD pallets

ULD pallets are aluminum sheets that can be loaded with cargo and securely lashed with netting. Also known as "cookie sheets" in the industry, pallets are designed to lock cargo in during transportation to prevent movement. There are multiple pallet types available, including single-layer and double-layer designs. Pallets are constructed in specific dimensions to meet known specifications.

Pallets are very lightweight compared to containers, which helps to lower costs and reduce labor requirements. ULD pallets accept a variety of oversized cargo, and they're especially useful for large and cumbersome loads that won't fit in a container. Pallets take up less room than containers, and their flat shape can be altered based on where they're loaded inside the plane.

Common ULD specifications

ULDs are constructed in multiple forms to meet diverse freight needs. Several types of containers and pallets are available, most of which are designed to fit several aircraft types. The maximum weights are general guidelines and can be 20-30% higher than what the ULD can realistically handle.

The most common ULD types include:


  • Volume: 159 cu. ft.

  • Dimensions: 79" x 60" x 64"

  • Contour: single

  • Max gross weight: 3,500 lbs


  • Aircraft: A300, A310, A330, A340, B747, 767, B777, DC-10, MD-11, 777, 787, A350


  • Volume: 256 cu. ft.

  • Dimensions: 125" x 60" x 64"

  • Contour: none

  • Max gross weight: 7,002 lbs


  • Aircraft: A300, A310, A330, A340, B747, B777, DC-10, D-11, 777, 787, A350


  • Volume: 316 cu. ft.

  • Dimensions: 160" x 60" x 64"

  • Contour: double

  • Max gross weight: 7,000 lbs


  • Aircraft: A300, A310, A330, A340, B747, B777, DC-10, MD-11, 777, 787, A350


  • Volume: 381 cu. ft.

  • Dimensions: 125" x 88" x 64"

  • Contour: none

  • Max gross weight: 13,227 lbs

  • IATA: P1P, AAP

  • Aircraft: A300, A310, A330, A340, B747, B777, DC-10, D-11, 777, 787, A350

LD-7 (aka PAG)

  • Volume: 379 cu. ft.

  • Dimensions: 125" x 88" x 64"

  • Contour: double

  • Max gross weight: 10,198 lbs

  • IATA: PAX, PAG, PAJ, PAP, P1A, PAA, P1C, P1D, and P1G

  • Aircraft: The lower deck of all wide-body aircraft

  • You can fit (4) 48x40 inch pallets on a PAG

PMC or P6P pallet

PMC or P6P aircraft pallet is a popular pallet type used to transport freight by air. This general-purpose flat pallet has universal application and is suited to lower holds and main decks. PMCs are often used to carry automobiles, motorcycles, and similar mechanical equipment, but they are not limited to this application. This ULD category features a lightweight aluminum construction made from high-strength 7000-series alloy. 125-88/96-inch pallets are common, with sheets clamped to edge rails using 45° chamfers and staggered rivets to enhance usability and service life.

  • Dimensions: 125" x 96" x 64”

  • Max gross weight: between 11,250 and 14,991 lbs (depending on air craft type)


  • Aircraft: A300, A310, A340, B747, B767, B777

  • You can fit (5) 48x40 inch pallets on a PAG

PGA pallet or PGE ULD

  • Dimensions: 238.5" x 96"

  • Max gross weight: 10,198 lbs

  • IATA: P7A, P7E, P7F, PSG, PGE, PGA

  • Aircraft: B747-MD (freighter), B777

Bulk unitization program (BUP)

Along with the containers and pallets listed above, freight forwarders can offer ready-made ULD solutions. Known as a BUP (bulk unitization program), these ready-to-load packages are built at the origin and sent as ready-to-ship units. BUPs offer many advantages, significantly reducing handling time at the cargo terminal by combining separate items into a single unit. For this reason, BUPs benefit from preferential conditions and rapid handling in busy airport environments. At the final destination, BUPs are turned over to the forwarder for unloading, often 3-4 days faster than airline-loaded ULDs.

ULD identification standards

Identification plays a central role in the air transportation sector. With huge volumes of containers and pallets in the air at all times, logistical solutions are needed to ensure seamless movement between processing points. A consistent and robust cargo identification system has been adopted for ULDs, with all containers identified by a unique three-section label. For example, AKE 12345 DL is a single ULD code.

The first section consists of a three-letter prefix to identify the ULD type and key characteristics. There are three positions, the 'ULD category,' the 'base code,' and the 'contour code.' These codes help industry workers to move and place containers effectively. For example, with the prefix 'AKE,' the 'A' in position 1 refers to the ULD category 'certified aircraft container,' the 'K' in position 2 indicates base dimensions of 1,534 × 1,562 mm (60.4 × 61.5 in), and the 'E' in position 3 refers to the contour of the container.

The second or middle section consists of a 4- or 5-digit serial number, which acts as a unique identification marker. If the container was constructed before October 1, 1993, it will have a 4-digit number. If the container was created after this time, it will either have a 4-digit number or a 5-digit number. This section is unique and helps to identify each ULD from others of the same type.

The third section consists of a two-character suffix, which is alpha-numerical. These letters are used to identify the ULD's owner. If the owner is an airline, this section is often the same as the International Air Transport Association's (IATA) designated code. This unique 3-letter code is used in logistics and aviation to identify an airport, such as 'JFK' for the John F. Kennedy International Airport in New York.

Benefits of ULDs

ULDs come in various shapes and sizes, making them ideal for countless applications. They can accommodate various freight types and fit into the cargo holds of many aircraft types. ULDs offer benefits for forwarders, shippers, and airlines, with the modular nature of loading and unloading providing new levels of efficiency and control for all parties. Despite the weight burden associated with ULD containers and pallets, they have become the recognized industry standard.

ULDs offer the following benefits:

  • Faster and more efficient loading and unloading.

  • Cargo is moved easily with specialized equipment.

  • Manual labor is significantly reduced when loading and unloading.

  • Preloaded units save time in aircraft turnaround and handling.

  • Aircraft cargo space is utilized much more effectively.

  • Cargo is transferred easily between aircraft and other transportation.

  • Cargo is locked in place, which secures freight and protects the aircraft.

  • Weight and balance disruptions are avoided during flight.

  • Massive cost savings are experienced in handling and transportation.

  • There is reduced fuel consumption due to optimized cargo space.

ULDs play a critical role in the air cargo industry, and they've become essential for the transportation of goods around the world. As competition grows between carriers and air freight schedules get more intensive, the intelligent utilization of ULDs will greatly influence future growth. Please Request a Quote if you have air freight consolidation requirements or Contact our team to learn more about ULDs and their many applications.



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