The shadow fleet, by flag

The "shadow fleet" — also called the dark or grey fleet — is the loose flotilla of mostly old tankers that carry sanctioned crude outside Western insurance, financing and the G7 oil price cap. It grew sharply after the 2022 sanctions on Russian oil, and it is now one of the most heavily covered subjects in maritime intelligence. It is also one of the most loosely quantified, because there is no single agreed definition of what belongs in it.

That is the first thing to get right. A number you read for the shadow fleet is only meaningful with its source and date — so we will pin both to every figure here.

The flag breakdown

In the KSE Institute analysis (figures as reported, drawn together with the Atlantic Council's coverage), the shadow fleet ran to 400-plus tankers, and the leading flags were:

Flag	Share of the fleet
Panama	17.3%
Liberia	12.4%
Russia	11.4%

The remainder is spread across a long tail of smaller registries, many of them obscure flags that appear and disappear as ships reflag to dodge attention. Note that two of the top three — Panama and Liberia — are also the two largest legitimate registries in the world, which is exactly why a flag alone never proves anything. The signal is in the combination: an old hull, an opaque owner, a recent reflag and an AIS record full of gaps.

An old fleet above all

The defining characteristic is age. Around 82% of the identified tankers were over 15 years old — vessels that would otherwise be heading for the scrapyard, given a second life moving barrels that the mainstream market will not touch. That ageing profile is the safety story: older tankers, often outside reputable class and insurance, carrying oil through busy straits, are the reason the shadow fleet is treated as an environmental risk and not merely a sanctions one. We cover the demographics in more detail in our piece on the ageing tanker fleet.

The shadow fleet is best understood not as a number but as a profile: an old hull, a flag of convenience, an opaque owner and a habit of going dark. KSE Institute / Atlantic Council analysis

Why the count keeps changing

Estimates for the shadow fleet range from 400-plus to well over 1,000 tankers, and both can be defensible at once. The spread comes from definition choices:

• Sanctioned only — count just the tankers explicitly listed by OFAC, the EU, the UK or others. This gives the tightest, smallest figure.
• Sanctioned trade — count every tanker observed carrying price-capped or embargoed crude, listed or not. This is much larger.
• Behavioural — count tankers exhibiting shadow-fleet behaviour (AIS manipulation, ship-to-ship transfers in odd places, no mainstream insurance), which is broader still.

Each definition answers a different question, so a headline figure with no methodology behind it is close to meaningless. This is why our broader explainer on the shadow fleet leads with the definition before any number.

How to check a single vessel

The shadow fleet is a population, but enforcement happens one hull at a time. To assess an individual tanker you screen it on the one identifier it cannot shed — its IMO number — against the sanctions lists, then read its age, flag history and ownership chain together. A clean name on a freshly reflagged 19-year-old tanker with an owner three shells deep is the pattern, not the proof.

That is what the Marifest registry is built to surface. Look up any vessel by name or IMO number and the file shows its flag, build year, ownership and a verdict from the compliance screen against the OFAC, EU, UN and UK lists — the structured, free lookup that the paywalled risk tools keep behind a login. For the how-to, see our guide on checking whether a ship is sanctioned.