Air freight capacity comes from two places: the cargo holds under the passenger cabin on scheduled flights (belly capacity), and aircraft built or converted to carry only cargo (freighters). Charter operations, ACMI leases and combi aircraft are variations on those two. For a shipper the source matters because it decides what size of piece fits, whether certain dangerous goods can fly at all, how often you can ship, and how badly your booking is exposed when the passenger schedule changes.
Most rate quotes never say which one you are buying. This guide explains the difference and lists the questions worth putting to a forwarder before you commit.
The two sources of capacity
Belly capacity
Passenger airlines carry cargo in the lower deck, the space under the cabin floor that also holds passenger baggage. The airline sells whatever room is left after bags. On a wide-body aircraft flying a long route, that can be a large amount of cargo space. On a narrow-body flying a short route, it is very little. Belly cargo is a by-product of a passenger schedule: the airline decides where and when to fly based on passenger demand, and cargo rides along.
Freighters
A freighter is an aircraft that carries only cargo, either built that way or converted from a passenger aircraft. It has a main deck (the space where passengers would normally sit) as well as a lower deck, so it can take larger pieces and more of them. Freighter operators and cargo airlines plan routes around cargo flows, not passenger demand, so their networks concentrate on big industrial and e-commerce lanes.
The variations you will hear about
- Combi aircraft: a passenger aircraft with part of the main deck given over to cargo. Rare today, but still the answer to some remote-route questions.
- ACMI (aircraft, crew, maintenance, insurance) leases: one company supplies the aircraft and crew, another sells the space. From the shipper's side it is still freighter capacity, just not always on the brand you expected.
- Charters: you or your forwarder book a whole aircraft for a specific movement. Our guide to air charter vs scheduled air freight covers when that is worth the cost.
How the split varies, and what we can and cannot say
The mix of belly and freighter capacity is not the same everywhere. It shifts with passenger schedules, aircraft deliveries and demand, and it differs by region and by lane: routes served mostly by passenger wide-bodies lean on belly space, while big cargo trunk lanes lean on freighters.
We are deliberately not quoting a percentage split. Widely repeated figures for the global belly share circulate without a clear source or date, and the numbers move from year to year. What can be sourced is direction of travel. IATA's air cargo market analysis for July 2026 (press release of 31 August 2026) reported total industry capacity up 1.7% on July 2025, with regional changes ranging from a 1.5% fall in North America to a 7.0% rise in Latin America, and said dedicated freighters gained market share as belly-hold traffic declined. If you need a current share for a specific region, IATA's monthly market analysis and data providers that track airline schedules publish it with an as-of date. Use a dated figure, not a remembered one.
Why it matters to a shipper
Piece size and weight limits
Lower-deck holds are shaped by the fuselage, with curved contours and doors sized for baggage and containers, so height and often piece size are limited. The main deck of a freighter is a much bigger space, and it can be loaded through a nose or side cargo door. The practical result is that a piece that has to be booked as main-deck cargo cannot go on a passenger flight, however good the schedule looks.
The exact dimensions and weight limits differ by aircraft type, and even by operator configuration, so there is no single number to quote. Ask your forwarder for the limit for the specific aircraft type on the specific flight, not a general rule. Our guide to air freight ULD types explains which unit load devices fit which decks, and the ULD types and dimensions reference is the place to check unit sizes.
Narrow-body bellies
Narrow-body passenger aircraft, which fly most short and medium routes, often carry cargo loose (bulk-loaded) or in a small number of units, and cannot take many of the larger ULDs. Pieces that fit a containerised wide-body hold may not fit here. If your shipment reaches its destination through a connection on a narrow-body leg, that leg can become the limit, even when the long-haul leg would have taken it comfortably. This is a common cause of an otherwise routine booking being re-routed or split.
Dangerous goods and Cargo Aircraft Only
Some dangerous goods are permitted only on freighters. The clearest example is lithium batteries shipped by themselves. IATA's lithium battery guidance document (edition dated 1 January 2026) states that lithium-ion cells and batteries shipped by themselves (UN 3480) are forbidden for transport as cargo on passenger aircraft, and that packages prepared under Packing Instruction 965, Sections IA and IB, must bear a Cargo Aircraft Only label. It says the same for lithium metal cells and batteries shipped by themselves (UN 3090, Packing Instruction 968) and for sodium-ion batteries shipped by themselves (UN 3551, Packing Instruction 976). It also notes that lithium metal batteries under Packing Instruction 968 may go on a passenger aircraft only in narrow cases involving approvals from the States concerned.
The consequence for capacity is direct: if your goods are Cargo Aircraft Only, only freighter flights are available to you, which means fewer departures and less choice of routing. This is a subset of the rules, not a substitute for them. Whether a given product falls under these packing instructions depends on its classification, its watt-hour rating and how it is packed, and the current Dangerous Goods Regulations govern. Read our guides on shipping lithium batteries by air and sea and IMDG and IATA dangerous goods regulations before you book, and have the declaration checked by a trained person.
Routing and frequency
Passenger networks are dense. A major hub-to-hub route may have several daily departures on different airlines, with many connections beyond, so belly capacity gives you frequency and reach to secondary cities. Freighters tend to operate point-to-point between large cargo hubs, often with fewer departures per week, between the same busy airport pairs. Freighters are the better tool for bulky, heavy or special cargo on trunk lanes. Belly space is often the better tool for small, urgent, frequent consignments to a wide range of destinations.
| Factor | Belly (passenger flight) | Freighter |
|---|---|---|
| Decks available | Lower deck only | Main deck and lower deck |
| Piece size | Limited by hold shape and door | Larger pieces possible, subject to the aircraft |
| Network | Follows passenger routes; many destinations and frequencies | Follows cargo flows; fewer airports, often point-to-point |
| Cargo Aircraft Only dangerous goods | Not allowed | Allowed, subject to the regulations |
| Exposure to passenger schedule changes | High | Low |
| Typical fit | General cargo, small to medium consignments | Heavy, large, special or Cargo Aircraft Only cargo |
How capacity shocks reach your rate
Because belly space is a by-product of passenger flying, a change to passenger schedules changes cargo supply immediately, without any change in cargo demand. Cuts to passenger flights, aircraft groundings and airspace closures all remove lower-deck space. Freighters do not disappear with the passenger schedule, but they are then asked to carry freight the bellies can no longer take, and they are a finite fleet.
The current picture shows this. IATA's July 2026 analysis says Gulf-linked corridors remained disrupted by the conflict in the Middle East, with the Europe-Middle East and Middle East-Asia trade lanes both contracting for a fifth consecutive month (as of the 31 August 2026 release). The same report noted that belly-hold traffic had declined while dedicated freighters gained market share. The situation is still moving, and we are not predicting where it goes.
What this tends to mean at the booking level:
- Rates on affected lanes usually rise, because the same demand is chasing less space. This is a tendency, not a promise of any particular level.
- Space allocations get tighter. Forwarders with long-term allocations on an airline may prioritise their regular customers over spot enquiries.
- Routings change. A shipment that would have flown direct may be routed through another hub, adding time and handling points.
- Cargo can be offloaded. If a flight is full or its loading changes, cargo can be moved to a later flight even with a confirmed booking.
Our Strait of Hormuz disruption playbook covers the Gulf situation for shippers in more detail.
Questions to ask your forwarder
- Is this space belly or freighter? If the answer is "it depends on the flight", ask which flight you are actually being quoted on.
- What is the aircraft type and the piece limit? Give the forwarder the exact dimensions of your largest piece, including packaging and pallet, and ask them to confirm it fits the deck and door on that aircraft.
- What ULD or loading method applies? Bulk loading in a narrow-body is a different proposition from a containerised wide-body.
- Do you accept main-deck cargo, and is it confirmed? Ask what "confirmed" means on this booking.
- Is any part of the route a passenger flight? A trunk freighter leg followed by a narrow-body connection changes the size limit.
- What is the offload risk and the fallback? Ask which flight your cargo would move to if it is offloaded, and who pays for any extra handling.
- Is the cargo dangerous goods, and does that limit the flights? Tell the forwarder before you ask for a rate, not after. If it is Cargo Aircraft Only, the flight options are narrower.
- What security screening applies? Requirements can differ by origin and route. See air cargo security, ACAS and screening.
What to do next
Before you ask for a quote, write down five facts: the dimensions and weight of your largest piece, the total number of pieces, whether any of it is dangerous goods, the latest acceptable delivery date, and whether the shipment can be split. With those in hand a forwarder can tell you quickly whether you need belly space or a freighter, and the quote is far less likely to change later. For how the price itself is built, see how air freight pricing works.
Finding a forwarder on CargoLinked
You can browse air freight forwarders by country or trade lane in the CargoLinked directory, or post your shipment on the requests board so that eligible forwarders can quote against the details you supply. Listings are self-published, so check a company's credentials and ask the questions above before you book. Quotes carry a validity date and expire after it, so confirm the space source and the aircraft limits while the quote is still valid.
