What is the dark fleet — and why it matters in 2026
The shadow fleet has grown to 600–800 tankers, roughly 10–15% of the global tanker fleet. Here is how it operates, why P&I withdrawal became the sharpest enforcement lever, and how exposure is detected.
For: Marine insurers, compliance, government
The “dark fleet” — or shadow fleet — is the fleet of tankers built to move sanctioned and price-capped oil without being seen. By early 2026 it numbered an estimated 600–800 vessels, roughly 10–15% of the world tanker fleet, and it has reshaped how sanctions are enforced and how maritime risk is priced.
How it operates
Dark-fleet vessels share a recognisable tradecraft:
- AIS manipulation. Transponders are switched off to create gaps around loading or transfer, or spoofed to broadcast a false position — circular tracks, “teleporting,” or land-locked coordinates.
- Ship-to-ship (STS) transfers in open water, often at night and away from normal transfer zones, to break the chain of custody on a cargo.
- Flag-hopping and opaque ownership. Frequent re-flagging and layers of shell companies obscure the beneficial owner behind a vessel.
- Questionable insurance. Cover from unknown or unrated providers, or forged certificates — by early 2026 roughly a third of tankers in some corridors were presenting sanctioned or Russian-linked insurance certificates.
Why P&I withdrawal became the key lever
Sanctions authorities learned that the most effective pressure point is not the cargo or the flag — it is the insurance. Protection and indemnity (P&I) cover is effectively mandatory for a tanker to trade and call at reputable ports. When the EU’s 20th sanctions package added 43 shadow-fleet vessels at once, it did more than name them: it stripped their access to legitimate cover.
That is precisely what makes accidental exposure existential for an insurer. Binding cover on a vessel that is later designated does not just create a bad risk — it can pull the insurer into the enforcement action.
The shift from reactive to predictive
Screening a vessel’s name against a sanctions list tells you about yesterday’s risk. The whole design of the shadow fleet is to stay off those lists — new shells, fresh MMSIs, re-flagging, carefully timed gaps. List-based screening is therefore structurally late.
The alternative is behavioural risk scoring: asking whether a vessel acts like one that is hiding something. AIS gaps normalised against expected satellite coverage, kinematically impossible positions that betray spoofing, loitering in transfer zones, and rendezvous with other high-risk tonnage all precede a designation rather than follow it. Fused with identity resolution across MMSI, IMO number and beneficial owner — and graph analysis of the ownership network behind a vessel — this turns “this ship looks risky” into “this ship sits inside a structure we have seen before.”
Corroborating with satellites
Behaviour is the first signal; imagery is the confirmation. When a vessel goes dark, synthetic aperture radar (Sentinel-1) still sees the hull, in any weather, day or night. A radar detection with no matching AIS return is a candidate dark ship — the same SAR-and-AIS fusion that underpins maritime domain awareness for governments.
This is the core of our dark-fleet and sanctions screening work: explainable, auditable risk scores that catch exposure before cover is bound, with the data lineage regulators and underwriters require.
Frequently asked
What is the dark fleet or shadow fleet? +
The dark fleet (also called the shadow fleet) is the group of tankers — estimated at 600–800 vessels, roughly 10–15% of the global tanker fleet — used to move sanctioned or price-capped oil while evading oversight. These ships typically use opaque ownership, obscure insurance, frequent re-flagging, and AIS manipulation to hide their activity.
Why does the dark fleet matter to insurers? +
Accidental exposure to a sanctioned or dark-fleet vessel is an existential compliance and reputational risk for a marine insurer. Withdrawal of P&I cover has become the single most powerful sanctions-enforcement lever, so binding cover on a vessel that is later designated can strip protection and trigger regulatory scrutiny.
How do you know if a vessel is part of the dark fleet? +
Dark-fleet vessels reveal themselves through behaviour — AIS gaps and spoofing, ship-to-ship transfers in unusual locations, flag-hopping, opaque or shell ownership, and mismatched or dubious insurance certificates. Behavioural risk scoring detects these patterns before a vessel appears on a designation list.