VI Energy Politics & Supply Security
Shadow fleet
A body of tankers with opaque ownership, mostly uninsured and with location signals switched off, operating to evade sanctions or safety, environmental and insurance rules.
How it works
The Assembly of the International Maritime Organization (IMO) defined these ships in resolution A.1192(33), adopted on 6 December 2023. Under the resolution, the shadow fleet comprises ships operating to evade sanctions or for other illegal activities. The same text notes that these ships deliberately switch off or manipulate their automatic identification system (AIS), the transponder that shows a ship's position to shore stations and satellites.
According to the March 2023 session of the IMO Legal Committee, the fleet numbers between 300 and 600 ships, most of them old tankers. The committee said these vessels are poorly maintained, have opaque ownership and are seriously underinsured. It singled out ship-to-ship transfers on the open sea as the riskiest operation; if an accident occurs, the cost of pollution falls on the coastal state.
Measurement holds two traps. A lost AIS signal is not by itself proof of illegal activity; the IMO resolution states that it is only a sign worth investigating. A sanctioned ship and a shadow-fleet ship are also not the same set: a listed tanker can run into insurer and port rules even when it carries cargo that is not under sanctions.
Why it matters here
The shadow fleet turns the price of sanctions into a question of ship supply. Every tanker placed on a list withdraws from lawful trade, and the usable fleet shrinks. In October 2026, after the transfer pattern outside Hormuz drove supertanker rates to a record, Washington began debating whether to let these ships carry oil that is not under sanctions. Sanctions, war and freight intersect on the same fleet; loosening one changes the cost of the others.