Air freight: paying a premium to compress time

Two very different sources of capacity

Most air cargo travels in the lower holds of passenger aircraft, where the space available depends on the passengers' baggage and the route's schedule rather than on cargo demand. Dedicated freighters carry cargo on the main deck as well, accept much larger pieces through wide doors, and fly patterns designed around freight flows. Belly capacity is plentiful and cheap on dense passenger routes and absent where passenger services are thin.

Density decides the charge

Aircraft are limited by both mass and volume, so carriers compare a consignment's actual weight with a figure derived from its dimensions and charge on whichever is greater. Light bulky freight is therefore rated on the space it occupies. The practical implication is that reducing the outer dimensions of a shipment can matter more than reducing its weight, and that generous void fill is charged for at air rates.

The hold is not a rectangular room

Fuselages are curved, so cargo is built onto unit load devices contoured to fit particular aircraft types, or into containers designed for specific holds. Pieces that cannot be built onto a device are loaded loose, which is slower and limited by door apertures and floor strength. A consignment that is too tall for a lower hold may still fly on a main deck, so the aircraft type available on a route determines what can be sent.

Security screening is a step, not a formality

Cargo carried on aircraft must be secured before it is loaded, either by screening it or by having originated within a supply chain of approved parties. Shippers accepted into such a scheme can present cargo already secure, which avoids screening methods that may be unsuitable for dense or sensitive goods. The framework is set by aviation authorities and reflected in the industry's cargo standards.

The flight is the short part

Elapsed time is dominated by the ground: road collection, acceptance and build-up at the origin terminal, waiting for a flight with space, break-down and release at destination, and final delivery. A shipment can spend far longer on the tarmac and in terminals than in the air, which is why door-to-door comparisons against other modes look very different from airport-to-airport ones.

Frequently asked questions

Why is a light shipment charged as though it were heavy?

Because volume is as scarce as mass on an aircraft. Carriers derive a weight from the consignment's dimensions and bill whichever figure is higher, so bulky low-density freight pays for the space it denies to something else.

Does air freight always beat sea on time?

On the moving leg, comfortably. Door to door the gap narrows, because collection, terminal handling, screening, flight availability and release at destination all take time regardless of how quickly the aircraft covered the distance.