Gold moving between continents usually flies, and it usually flies underneath passengers on scheduled commercial services. The reasoning is practical and explains why airline route networks shape metal flows.
The cargo is small, heavy and extremely valuable
A shipment worth an enormous sum can occupy a volume smaller than a few suitcases. Gold is dense, so weight rather than space is the binding constraint.
That profile fits the belly hold of a passenger aircraft, which has weight capacity available on most routes and does not require chartering a dedicated freighter.
Chartering exists for very large movements, but for routine flows the incremental cost of a belly-hold slot is far lower.
Scheduled services offer predictable security
Passenger flights run to fixed timetables on established routes with known ground handling at both ends. Secure transport firms can plan armored road legs against a published arrival time.
Predictability matters more than speed here. A shipment that lands as expected can be moved directly into a vault with a security detail already waiting.
Frequency helps too, since a missed connection on a daily service costs a day rather than a week.
Insurance underwriters shape the routing
Specialist insurers set the terms under which valuable cargo is covered, and those terms often specify permitted carriers, routes, transfer points and a maximum value per aircraft.
A single flight may therefore carry only so much value, which forces larger consignments to be split across multiple departures.
Those rules explain otherwise puzzling routings, where metal travels via a hub that looks indirect on a map but satisfies the coverage conditions.
Route networks become metal corridors
Because shipments depend on scheduled capacity, gold flows concentrate along the same city pairs that carry heavy passenger traffic between financial and refining centers.
Cities with strong long-haul connectivity and established customs handling for precious metals accumulate a share of the trade that reflects their airline networks as much as their vaults.
When flight schedules contract, as they did during widespread aviation disruption, physical metal movement becomes slower and more expensive almost immediately.
Why this shows up in prices
Regional price differences persist only while metal cannot be moved cheaply to close them. Freight and insurance costs set the width of the band inside which those differences can survive.
If moving an ounce between two markets becomes costly, the two markets can drift further apart before anyone finds it worthwhile to ship.
Transport is therefore not a background detail of the metals trade but one of the mechanisms that keeps prices in different countries tied together at all.