Most Air Freight Travels Under Passengers Who Never Know
A large share of air cargo moves in the hold of passenger aircraft flying anyway, at close to zero marginal cost. That capacity appears and disappears with passenger schedules, which makes the freight market unusually unstable.
Two Sources of the Same Capacity
Air cargo travels two ways. Belly capacity is space in the hold of a passenger aircraft that is flying regardless. Freighter capacity is a dedicated cargo aircraft, either purpose built or a converted passenger airframe.
Historically belly capacity has accounted for roughly half of global air cargo, concentrated on long haul routes where widebody aircraft carry substantial hold volume.
The economics of the two are entirely different, and that difference explains nearly everything about how the market behaves.
The Marginal Cost Asymmetry
A passenger aircraft flies because passengers bought tickets. The fuel, crew, and airport costs are incurred for that purpose.
Carrying cargo in the hold adds weight, which burns some additional fuel, plus handling cost. That is genuinely the marginal cost, and it is small relative to the revenue.
A freighter operator has no such subsidy. Every cost of the flight must be recovered from cargo alone.
| Belly Capacity | Freighter | |
|---|---|---|
| Marginal cost of carrying cargo | Low | The entire flight cost |
| Schedule driven by | Passenger demand | Cargo demand |
| Routes served | Passenger city pairs | Wherever freight wants to go |
| Behaviour in a downturn | Disappears with the flights | Can be parked or redeployed |
A freighter operator competes against capacity whose cost was already paid by somebody else. That is a permanent structural disadvantage in normal conditions and it reverses completely whenever passenger flying stops.
Why the Market Is So Volatile
Because roughly half the supply is a byproduct of an unrelated business, air freight capacity moves for reasons having nothing to do with freight demand.
The clearest demonstration came in 2020. Passenger flying collapsed, removing an enormous share of global cargo capacity within weeks, while demand for urgent shipments of medical supplies and electronics rose.
Rates increased by multiples. Airlines responded by operating passenger aircraft with empty cabins purely for hold cargo, and in some cases removing seats to load freight in the cabin, an arrangement requiring regulatory approval and previously almost unknown.
Freighter operators experienced extraordinary profitability during precisely the period their competitors were grounded, and the subsequent recovery in passenger flying returned capacity and normalised rates.
What Moves by Air and Why
Air freight carries a very small share of world trade by weight and a substantial share by value, which tells you what qualifies.
The economics require that the value of speed exceed the cost premium over ocean freight, which is roughly an order of magnitude. That is satisfied by high value electronics, pharmaceuticals requiring temperature control and rapid delivery, perishables including flowers and seafood, urgent spare parts where an aircraft or a factory is idle, and fashion where a season is short.
The category that grew fastest is cross border direct to consumer parcels, where individual shipments are small, valuable relative to weight, and time sensitive because the customer is waiting.
The Conversion Market
Because purpose built freighters are expensive and produced in small numbers, a substantial part of the fleet consists of converted passenger aircraft, retired from passenger service and modified with a main deck cargo door, a reinforced floor, and cargo handling systems.
The conversion economics depend on the price of retired airframes, which falls when airlines retire fleets, and on freight rates. The result is a countercyclical relationship: aircraft become cheap to convert at exactly the point when passenger demand is weak, which is frequently when freight is strong.
Conversion capacity itself became a constraint during the demand surge, with slots at conversion facilities booked years ahead.
The Integrator Model
A distinct category operates outside the ordinary market. Integrated express carriers own aircraft, ground fleets, and sorting hubs, and sell a delivery service rather than transport capacity.
Their networks are built around overnight hub sorting, with aircraft flying at times dictated by the sort schedule rather than by point to point demand. That is a fundamentally different asset utilisation model, and it means their aircraft are not substitutes for general freight capacity even though they carry cargo.
How to Read the Market
The indicators that matter are the ratio of freight capacity to demand, usually expressed as a load factor; the share of capacity coming from belly versus freighters, since a belly heavy market is more exposed to passenger schedule changes; and the direction of passenger widebody capacity growth, which is a leading indicator of freight rate pressure.
Freighter operators are best analysed as a levered bet on the gap between the two, and their strongest periods are the ones when their competitors have stopped flying.
The Bottom Line
Air cargo is supplied half by aircraft flying for another reason entirely, at close to zero marginal cost, and half by freighters that must recover everything from cargo. That split makes capacity respond to passenger demand rather than freight demand, which is why rates move by multiples rather than percentages when passenger flying changes. Any assessment of a freighter operator should begin with what the passenger widebody fleet is doing, because that is the supply curve it competes against.