Which mode of freight transport is the most expensive per ton-mile?

The freight transport mode that is generally most expensive per ton-mile is air freight.

Aircraft move cargo rapidly over long distances, but that speed comes with high operating costs. Fuel, aircraft ownership, crew, airport handling, security, and limited cargo capacity all contribute to higher unit costs than those of ships, trains, or trucks. Air freight is therefore used mainly for high-value, lightweight, urgent, or perishable goods rather than bulk commodities.

The usual cost ranking places sea freight at the low end, followed by rail and road in many long-distance comparisons, with air at the high end. The exact order between road and rail can change with distance, shipment size, terrain, infrastructure, and pickup or delivery requirements. Air freight’s cost also varies substantially by aircraft type, route, fuel prices, dimensional weight, and whether the shipment uses a dedicated cargo plane or spare capacity on a passenger flight.

A related mix-up is confusing cost per ton-mile with total shipment price. A short air shipment may cost less in absolute terms than a very long ocean movement, but air remains the most expensive major mode when comparing the cost of moving a ton over one mile. Its advantage is speed, not economy.