What air freight is really bought for
Speed is the obvious answer and it is incomplete. What air freight actually sells is the ability to compress a decision that was taken late, and to do it on frequent, scheduled departures. A supply chain that plans well rarely needs it; a supply chain that has just discovered a problem needs nothing else.
That is why the economics are judged against the cost of not having the goods rather than against the cost of another mode. A production line standing idle, a seasonal window closing, a replacement part holding up an installation, a launch date that cannot move — in those cases the freight premium is small against what it prevents. Where the goods could equally arrive later, air freight is an expensive way to buy reassurance.
Air is also used structurally rather than in emergencies: for goods with a very high value relative to their weight, where the capital tied up in a long transit costs more than the flight, and for goods with a short usable life.
Chargeable weight: the most misread part of an air quote
An aircraft runs out of space and out of weight allowance, and either can be the binding limit. So air freight is not charged on actual weight alone. A volumetric equivalent is calculated from the outer dimensions of the shipment using a conversion set by the carrier or by the agreement in force, and the charge is based on whichever is greater: the actual gross weight or that volumetric figure.
Two consequences follow, and both are actionable. Light, bulky cargo is charged as though it were heavier, which means reducing the packed dimensions can reduce the cost even though nothing has been removed from the shipment. And the measurement is of the shipment as presented for carriage — including the pallet, the crate, the protective frame and any overhang — not of the goods as they left the production line.
The conversion used, how measurements are rounded and how a shipment of mixed packages is treated all vary by carrier and by agreement. They are confirmed for the specific booking. What does not vary is the principle, and a shipper who understands it will design packaging differently.
- Measure and declare packed dimensions, including pallets and protective structures
- Expect the shipment to be reweighed and remeasured at acceptance
- Reducing height or overhang on a light shipment can change the charge
- Packaging is charged like cargo, so it must be strong without being heavy or oversized
The flight is a small part of the elapsed time
Between a collection address and a delivery address, the time spent airborne is usually the shortest identifiable segment. Around it sit the road leg to the airport, the acceptance cut-off, screening, the building of the cargo onto aircraft-suitable units, documentation, any formalities at both ends, breakdown and release at destination, and the road leg out.
That is why door-to-door air freight is judged end to end. Two options with the same flight can behave very differently once the ground handling and the road legs are compared, and a plan that fails almost always fails on the ground rather than in the air.
It also explains the value of readiness. Cargo that arrives at the airport correctly packed, correctly labelled and with its documentation complete moves through acceptance; cargo that does not waits, and the wait is measured against departures rather than hours.
Capacity is not uniform, and it moves
Air cargo travels in the lower hold of passenger aircraft and on dedicated freighters. Hold capacity on a passenger flight is what remains after passengers, baggage and fuel requirements are met, so it varies by aircraft type, by route and by day rather than being a fixed quantity. Freighters carry loads on the main deck that a passenger aircraft simply cannot accept.
This has practical consequences for planning. The shape and size a shipment may take depend on the aircraft and on the units cargo is built onto, and loads that exceed the contour of a hold need a different aircraft rather than a different booking. Capacity also tightens seasonally and on imbalanced routes, where the direction with the demand is harder to buy.
None of this is knowable from a schedule. What can be carried, on what, and when, is established at booking for the specific shipment.
What cannot simply be handed over
Air carriage applies strict rules to goods that present a hazard, and acceptance depends on correct classification, packing, marking and declaration by people trained to do it. A shipment that is wrongly described can be refused at acceptance, removed from a build, or worse.
The recurring problem is goods that a shipper does not think of as hazardous. Lithium batteries are the clearest example — shipped alone, installed in equipment, or packed alongside it — and there are others: aerosols, some adhesives, paints and solvents, magnets, equipment containing fuel or residues, and some chemicals present in small quantities within a larger consignment.
What applies depends on the commodity, the packaging, the carrier and the jurisdictions involved, and it changes. The requirement is to establish it before booking with the carrier or an appropriately qualified party, and to describe the goods accurately rather than in the commercial terms used on a purchase order.
Packing for air is its own discipline
Air cargo is handled more than it is carried: built onto units, moved between them, loaded, unloaded and broken down again. It also experiences pressure and temperature changes that road freight does not.
The design goal is therefore strength without weight and without wasted volume, since both are charged. Compact, square packages build efficiently onto aircraft units; irregular shapes and overhang waste space that somebody pays for. Under-packing to save chargeable weight is a false economy, because the loss it eventually causes is larger than the saving it produced.