---
title: "See unit load device"
description: "Free space above a liquid contained in a tank  drum or tank-container  expressed as a percentage of the total capacity."
url: "https://oceancargo.co.uk/shipping-terms/see-unit-load-device"
date: "2026-05-25T12:13:17+00:00"
language: "en-GB"
---

![Ocean Cargo](https://oceancargo.co.uk/images/GenPics/OCs-Customs-Brokerage.webp)

 # Understanding ULDs and Headspace in Global Freight

## What is a Unit Load Device (ULD)?

In the intricate world of air freight, efficiency and cargo safety are paramount. This is where the Unit Load Device, or ULD, plays a critical role. A ULD is essentially an item of equipment used to consolidate and contain cargo, making it easier to load, transport, and unload on aircraft. Think of them as the building blocks of air cargo, designed to fit precisely into an aircraft's cargo hold.

ULDs come in two primary forms: aircraft pallets and aircraft containers. Both are engineered to specific dimensions and weight capacities, ensuring optimal use of space and structural integrity during flight. Ocean Cargo leverages a deep understanding of ULD specifications to maximise cargo efficiency and minimise costs for our clients, whether you're shipping [air freight to the USA](https://oceancargo.co.uk/countries/usa/air-freight-usa) or any other global destination.

## Types of Unit Load Devices (ULDs)

The variety of ULDs available caters to different aircraft types and cargo requirements. Understanding these types is crucial for efficient air freight planning:

- **Aircraft Pallets:** These are robust, flat platforms, typically made of aluminium, onto which cargo is loaded and then secured with nets and straps. Common pallet types include the PAG (88 x 125 inches) and the PMC (96 x 125 inches), designed to fit wide-body aircraft.
- **Aircraft Containers (Igloos):** These are enclosed containers, often made of aluminium or fibreglass, shaped to fit the contours of an aircraft's fuselage. They offer enhanced protection for cargo and come in various sizes, such as the AKE (a common lower-deck container) and the larger M-type containers for main deck loading.
- **Specialised ULDs:** For specific cargo needs, there are refrigerated ULDs for temperature-sensitive goods, and open-top ULDs for oversized items that can't fit through standard container doors.

Choosing the correct ULD is a critical step in the air freight process. It impacts not only the safety and security of your goods but also the overall cost and efficiency of the shipment. Our [air freight services](https://oceancargo.co.uk/services/air-freight/) team at Ocean Cargo provides expert guidance on ULD selection, ensuring your cargo is always handled with the utmost care and precision.

## Benefits of Using ULDs in Air Freight

The widespread adoption of ULDs in air cargo logistics is due to their numerous advantages:

- **Enhanced Cargo Protection:** Containers offer a protective shell against external elements and potential damage during transit and handling. Pallets, when properly netted, also provide significant stability.
- **Improved Efficiency:** ULDs allow for rapid loading and unloading of aircraft, significantly reducing ground time and improving turnaround efficiency for airlines. This translates to faster transit times for your goods.
- **Optimised Space Utilisation:** Designed to fit aircraft contours, ULDs maximise the use of available cargo space, which can lead to more competitive freight rates.
- **Increased Security:** Once sealed, ULDs provide an additional layer of security against tampering and theft, a crucial consideration for high-value or sensitive shipments.
- **Streamlined Handling:** ULDs are easily moved with specialised ground support equipment, simplifying the handling process at airports and reducing the risk of manual handling errors.

Ocean Cargo understands that every shipment is unique. Our expertise in ULD management ensures that your cargo, whether it's delicate electronics or heavy machinery, benefits from these advantages, providing you with peace of mind and reliable delivery.

## Navigating ULD Regulations and Compliance

The use of ULDs is governed by strict international regulations, primarily set by the International Air Transport Association (IATA) and national aviation authorities. These regulations cover everything from design and [Manufacturing](https://oceancargo.co.uk/industries/manufacturing-industrial "Manufacturing") standards to maintenance, repair, and operational procedures.

Key aspects of ULD compliance include:

- **Certification:** All ULDs must be certified to meet specific airworthiness standards.
- **Weight Limitations:** Each ULD has a maximum gross weight, which must never be exceeded. This includes the tare weight of the ULD itself plus the weight of the cargo.
- **Loading Procedures:** Specific guidelines dictate how cargo should be loaded and secured within a ULD to ensure stability and prevent shifting during flight.
- **Maintenance:** Regular inspections and maintenance are mandatory to ensure ULDs remain in safe and serviceable condition.

Non-compliance can lead to significant delays, fines, and even safety hazards. Ocean Cargo's [customs compliance](https://oceancargo.co.uk/services/customs-compliance/) and air freight specialists are well-versed in these regulations, ensuring that all shipments handled by us adhere to the highest standards of safety and legality, from [air freight to Canada](https://oceancargo.co.uk/countries/canada/air-freight-canada) to complex [project logistics](https://oceancargo.co.uk/services/project-logistics "project logistics").

## Understanding Headspace in Liquid Cargo Shipping

While ULDs are specific to air freight, another critical concept in the shipping of liquids, particularly in sea freight and road freight, is 'headspace'. Headspace refers to the free space above a liquid contained in a tank, drum, or tank-container, expressed as a percentage of the total capacity. It's a seemingly simple concept with profound implications for safety, compliance, and cargo integrity.

The presence of headspace is not merely an oversight; it's a deliberate and essential safety measure. Liquids, unlike solids, expand and contract with changes in temperature. Without adequate headspace, a liquid could expand to the point of over-pressurising its container, leading to leaks, ruptures, or even explosions. This is particularly critical for hazardous materials or temperature-sensitive liquids.

Ocean Cargo's expertise extends to the safe and compliant transport of liquid cargo, ensuring that appropriate headspace is always maintained, whether you're shipping chemicals, oils, or other bulk liquids via [sea freight](https://oceancargo.co.uk/services/sea-freight/) or [road freight](https://oceancargo.co.uk/services/road-freight/).

## Why Headspace is Crucial for Liquid Shipments

The importance of maintaining correct headspace cannot be overstated, especially when dealing with international shipping where cargo can experience significant temperature fluctuations:

- **Thermal Expansion:** Liquids expand when heated. If a container is filled to 100% capacity at a cooler temperature, it will likely burst or leak when exposed to warmer conditions during transit.
- **Vapour Pressure:** Many liquids, especially volatile ones, generate vapours that exert pressure within the container. Headspace allows for the safe accumulation of these vapours without exceeding the container's pressure limits.
- **Sloshing and Dynamic Loads:** During transit, particularly on ships or lorries, liquids can slosh around. Headspace helps to mitigate the impact of these dynamic forces, reducing stress on the container walls and preventing damage.
- **Safety and Compliance:** Regulations for shipping [Dangerous Goods](https://oceancargo.co.uk/services/specialised-services/specialised-services-dangerous-goods "Dangerous Goods") often specify minimum headspace requirements to prevent incidents. Non-compliance can lead to severe penalties and environmental hazards.
- **Product Integrity:** For certain products, maintaining a specific headspace can be crucial for preserving product quality, preventing oxidation, or allowing for necessary gas exchange.

Ocean Cargo works closely with clients to determine the optimal headspace for their specific liquid cargo, taking into account the nature of the liquid, the type of container, and the expected transit conditions. This meticulous planning is part of our commitment to delivering your cargo safely and efficiently, even for complex shipments like [excavators and diggers to the UAE](https://oceancargo.co.uk/countries/uae/excavators-diggers-uae), which might involve associated liquid fuels or lubricants.

## Calculating and Managing Headspace

The calculation of required headspace is a precise science, often dictated by the specific properties of the liquid (e.g., coefficient of thermal expansion, vapour pressure) and the expected temperature range during transit. Industry standards and regulatory bodies provide guidelines for various classes of goods.

Key considerations in managing headspace include:

- **Product Data Sheets:** Always refer to the Safety Data Sheet (SDS) or Technical Data Sheet (TDS) for specific liquid properties and recommended filling levels.
- **Container Type:** The design and material of the tank, drum, or IBC (Intermediate Bulk Container) will influence how much pressure it can safely withstand.
- **Route and Season:** A shipment from the UK to Australia will experience vastly different temperatures than one to Northern Europe, requiring different headspace considerations.
- **Regulatory Requirements:** For [Dangerous Goods](https://oceancargo.co.uk/services/specialised-services/specialised-services-dangerous-goods "Dangerous Goods"), specific regulations (e.g., IMDG Code for sea freight, ADR for road freight) will mandate minimum headspace percentages.

Ocean Cargo's [project logistics](https://oceancargo.co.uk/services/project-logistics "project logistics") team has extensive experience in handling specialised cargo, including liquids. We provide comprehensive advice and solutions to ensure that your liquid shipments are packed, loaded, and transported in full compliance with all safety and regulatory requirements, safeguarding your cargo and reputation.

#### What is the main difference between an aircraft pallet and an aircraft container (ULD)?

An aircraft pallet is a flat platform onto which cargo is secured with nets, while an aircraft container is an enclosed, rigid unit, often shaped to fit the aircraft's fuselage, offering more protection.

#### Why is headspace so important for liquid cargo?

Headspace is crucial because liquids expand with temperature changes. Without sufficient free space, the liquid could over-pressurise its container, leading to leaks, ruptures, or explosions, especially during transit.

#### Can ULDs be used for sea freight?

No, ULDs are specifically designed and certified for air freight to fit aircraft cargo holds. Standard shipping containers ([FCL](https://oceancargo.co.uk/services/sea-freight "FCL")/[LCL](https://oceancargo.co.uk/services/sea-freight "LCL")) are used for sea freight.

#### Who is responsible for ensuring correct headspace in a liquid shipment?

The shipper is primarily responsible for ensuring the correct filling level and headspace. However, a reliable freight forwarder like Ocean Cargo will provide expert guidance and verify compliance to prevent issues.

#### How does Ocean Cargo help with ULD selection and headspace management?

Ocean Cargo's experts provide consultative advice on selecting the most appropriate ULD for air freight based on cargo type and aircraft, and for liquid shipments, we guide clients on optimal headspace requirements to ensure safety and compliance.

### Ready to simplify your global logistics?

Get advice and a quote for your next shipment. Contact the Ocean Cargo team to start shipping.

[Freight Quote](https://oceancargo.co.uk/contact-us)

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