Cargo aircraft: how they work, the world's largest, and what it means for shipping from Brazil

A cargo aircraft is any plane that carries goods, either a dedicated freighter with no passengers or the belly hold of a scheduled flight. Cargo travels on standardised pallets and containers called ULDs. By capacity, the largest freighter in commercial service is the Antonov An-124, which carries up to 150 tonnes, according to its Ukrainian manufacturer.

When your box leaves a pickup in São Paulo bound for Tokyo, nobody books a plane for it. It goes onto a pallet, the pallet goes into a hold, and the hold is shared with hundreds of other shipments. Knowing how that machine works helps you pack better, forecast cost and understand why some cargo stays on the ground.

How does a cargo aircraft work?

A freighter is an aircraft whose passenger cabin has been replaced by an open main deck, a roller floor, pallet locks and a wide cargo door, either on the side or in the nose. Below it sits the lower deck, the same hold that carries luggage on a passenger jet. The crew is minimal and the whole fuselage becomes cargo space.

Some freighters leave the factory that way. Others start life as passenger jets and are converted years later: Boeing, for example, offers converted versions of the 767-300 and 737-800 alongside its production freighters. Source: Boeing, October 2026.

The hold of passenger flights, known in the trade as "belly" capacity, also carries goods on every commercial route. The difference is control: on a passenger flight, cargo adapts to the timetable, the weight of the bags and the size of the door. On a freighter, the flight exists because of the cargo.

Which are the largest cargo aircraft in the world?

The largest cargo aircraft ever built was the Antonov An-225 Mriya, 84 metres long with an 88.4-metre wingspan. In 2004 it flew 247 tonnes of cargo from Prague to Tashkent and set six world records. Source: Antonov, October 2026.

The table compares the biggest freighters by what matters to shippers: how much weight they lift. Figures are those published by the manufacturers.

The Mriya has a link to Brazil. In 2016 it carried a 155-tonne electric turbine, housed in a 27-tonne frame, from São Paulo to Santiago, Chile: a single 182-tonne load. Source: Antonov, October 2026.

In day-to-day trade, though, the world is carried by mid-size and large freighters such as the 777F and the 767-300F, flying scheduled routes every day. The Antonov giants take what fits nowhere else: turbines, generators, power plant parts.

What is a ULD and how is cargo arranged inside the aircraft?

A ULD (unit load device) is the pallet with its restraint net, or the aircraft container, on which cargo is built up before loading. Under the definition of IATA, the airline industry association, it is an aircraft part: it must hold the cargo in flight and protect the airframe.

IATA estimates about 1 million ULDs in service worldwide, with a replacement value above USD 1 billion. Source: IATA, October 2026. Each type has its own contour, which follows the curve of the fuselage. That is why a box that is too tall may fit on a truck and still not fit on a lower-deck pallet.

For shippers the lesson is practical. A well-palletised load, kept inside the pallet base with no overhang, goes into the ULD build-up without rework. The step-by-step is in the guide on how to palletise cargo in Brazil.

How much weight fits in a cargo aircraft, and what limits a shipment?

The limit is twofold: weight and volume. A large freighter rarely takes off at maximum weight when it carries light, bulky cargo, because the space runs out first. A load of pillows fills the deck with little weight. A load of engines does the opposite.

That is why air freight charges the greater of actual weight and volumetric weight, which converts volume into kilos. The formula and the tweaks that lower chargeable weight are in the guide to volumetric weight in Brazil.

Other limits appear before the flight: the size of the cargo door, floor strength per square metre and the rules for dangerous goods, which only fly when classified, packed and declared. The full air shipment process, from booking to delivery, is in the guide to air cargo transport in Brazil.

How does an express network run its aircraft fleet?

An express network blends its own aircraft, from airlines it controls, with space bought from other carriers, adjusting capacity to each day's volume. DHL Express reports more than 275 dedicated aircraft, operated by in-house airlines, some majority-owned by the group, and partners, serving more than 220 countries and territories. Source: DHL Group, October 2026.

The design is hub-based. Shipments from each region converge on a sorting centre, change aircraft and fly on to destination. DHL names three global hubs: Leipzig in Germany, the largest in the network and running since 2008, Hong Kong and Cincinnati in the United States. In Leipzig a shipment takes on average two hours to be unloaded, re-sorted and loaded again. Source: DHL, October 2026.

Spare capacity on the network's own flights is sold as general air cargo. That is how an express freighter can fly full on every leg of a route, not just the busiest one.

What does this change for businesses shipping by air from Brazil?

It changes how you prepare the shipment. Three habits prevent most problems:

1. Measure and weigh every package before pickup, because the carrier re-weighs and re-measures, and any difference is billed.
2. Palletise heavy loads, with weight concentrated at the base and nothing hanging over the pallet edges.
3. Declare the exact contents on the invoice, including batteries and perfumes, which follow their own boarding rules.

For loads from 50 kg to 3,000 kg, express also works, with palletised pieces of up to 1,000 kg, according to the service material published by DHL Express in 2026. Details are in the guide to Heavy Weight Express in Brazil.

Frequently asked questions about cargo aircraft

Sources

• Antonov: AN-225 Mriya, history and specifications
• Antonov: AN-124 Ruslan, history and specifications
• Boeing: Freighters, 777-8F, 777F and 767-300F specifications
• Boeing: 747-8 Freighter, press release of 6 March 2008
• IATA: Unit Load Devices (ULD)
• DHL Group: Express division, key figures
• DHL: DHL Hub Leipzig, location
• DHL Express: Heavy Weight Express service guide (pt-BR)
• Smithsonian Magazine: Ukrainian officials say the world's largest aircraft, Antonov AN-225, has been destroyed

Put your cargo on a network that flies every day

If your business sends samples, parts or palletised batches out of Brazil, or receives them from abroad, the shortest route is direct access to an express air network. Open a DHL Express business account and quote your next shipment with pickup, flight, clearance and delivery in a single service.