Air freight is chosen for high-value, light, urgent or short-shelf-life cargo; sea freight for heavy, bulky cargo with a low value per kilogram and a flexible delivery date. The decision is not made on freight alone: transit time, capital tied up in stock, cargo density, damage risk and carbon emissions are assessed together.
The basic trade-off: speed versus unit cost
Air freight delivers door to door within days; sea freight takes weeks over the same distance. In return, the cost of carriage per tonne by sea is much lower. According to IATA, air cargo carries roughly one third of world trade by value, while its share by tonnage is very small. This picture shows the general rule: air is the mode for valuable, time-sensitive cargo, sea for bulky and heavy cargo.
Criteria to consider when deciding
- Urgency: A spare part for a stopped production line or a product with a fixed campaign date can justify the speed difference on its own.
- Value per kilogram: As value rises, the ratio of freight to the value of the goods falls and air becomes reasonable.
- Cargo density: Cargo below roughly 167 kg per cubic metre is charged by volume in air freight; see chargeable weight.
- Inventory cost: A long transit time means capital tied up in goods on the way and a need for safety stock.
- Size and weight: Aircraft doors and ULD contours set limits; for very large pieces see heavy cargo by air.
- Dangerous goods: IATA DGR applies in the air, IMDG at sea; some substances may only be carried on cargo aircraft or are not accepted at all. The rule sets are compared side by side in the ADR, RID, IMDG and IATA DGR comparison.
- Carbon: Emissions per tonne-kilometre are many times higher in the air than at sea; the calculation method is in the entry carbon emission calculation.
Comparison table
| Criterion | Air freight | Sea freight |
|---|---|---|
| Transit time | Days | Weeks |
| Unit cost | High | Low |
| Suitable cargo | Electronics, pharmaceuticals, spare parts, samples, perishables | Raw materials, machinery, furniture, bulk and voluminous cargo |
| Size limit | Limited by the aircraft door and ULD | Wide, with containers, RoRo and conventional vessels |
| Transport document | AWB, non-negotiable | Bill of lading, may be negotiable |
| Carbon emissions | High | Low |
How do you compare total cost?
- Work out the gross weight, dimensions and chargeable weight of the cargo.
- Obtain door-to-door transit time and all charges (pre-carriage, terminal, customs, final delivery) for both modes.
- Calculate what the difference in days means in inventory, financing and lost sales.
- Add the difference in packaging and insurance; sea freight usually requires more robust packaging.
- Split the shipment if necessary: send the urgent part by air and the rest by sea.
Options in between
In a sea-air combination, the cargo first travels by ship to a transhipment hub and from there by aircraft to the destination; time and cost fall between the two modes. For cargo going from Türkiye to Europe, the Middle East, Russia and Central Asia, road freight is often a middle way that should be assessed separately: it carries door to door and needs no transhipment. In sea freight, choosing FCL or LCL according to the cargo volume also changes the cost significantly.
Common mistakes
- Comparing only the per-kilogram freight and leaving out door-to-door charges
- Choosing sea freight without accounting for the cost of delay
- Pricing bulky but light cargo on gross weight
How does Voltim Global support you?
Voltim Global assesses the air freight and sea freight options for the same cargo, together with a road alternative where needed. Air freight is planned with partner airlines and agents, sea and road transport with contracted carriers; the customer works with a single point of contact.