1. What the shadow fleet is, in one paragraph
The shadow fleet is the collection of tankers, mostly 15 to 25 years old, that carry sanctioned Russian, Iranian and Venezuelan oil outside Western insurance and registry standards, often switching flags, going dark on AIS and transferring cargo ship to ship at sea. How many ships that actually is depends on who is counting: Ukraine's military intelligence service (GUR) lists 1,337 vessels as of February 2026, while the Atlantic Council counted around 1,140 as of August 2025. Both figures are given below, not averaged, because they use different catalogues and cut-off dates.
This entry is about the ships: their age, their insurance, why some go dark, and what happens when one has an accident. Our sanctions-shadow entry covers the trading side, the price cap and how sanctioned oil actually gets sold; the two are meant to be read together, not as duplicates.
2. How a shadow fleet tanker actually operates
Four features distinguish a shadow fleet tanker from an ordinary one: an old hull, thin or missing insurance, a habit of switching off tracking, and cargo transfers at sea that break the paper trail. Age comes first: shadow fleet tankers are mostly 15 to 25 years old, well past the age major oil companies typically prefer to charter (shipfinex.com, 2026), which matters for everything that follows because older hulls carry more structural and mechanical risk.
Insurance is the second gap. Many of these ships sail without cover from the International Group of P&I Clubs, the network that normally backs the world's tanker fleet, relying instead on smaller, non-IUMI clubs, or in documented cases no insurance at all (shipfinex.com, 2026). The Atlantic Council found that by the end of February 2026, roughly a third of tanker transits through the Baltic Sea used sanctioned Russian or Russia-linked insurers rather than Western cover, a gap that also shows up in how a normal tanker's war risk premium is priced, since that pricing assumes recognised P&I cover in the first place.
Third, operators switch off the AIS transponder while loading at sanctioned terminals, and some also broadcast false positions while actually loading there (shipfinex.com, 2026). Windward defines "prolonged dark activity" as three or more days with no signal (11 August 2026). Fourth, cargo is transferred ship to ship on the open sea, usually at an anchorage outside a major port, specifically to break the documented chain between loading port and end buyer (shipfinex.com, 2026), a tactic that sits outside the legitimate freight market our tanker freight rates entry describes.
A documented case from Windward: the Russian-flagged Aframax tanker "TRUST" (IMO 9382798), which had changed its MMSI and flag six times since December 2025, carried out a "semi-dark" ship-to-ship transfer of about 325,000 barrels of Russian crude with a non-transmitting vessel in Omani territorial waters on 3 March 2026 (Windward Knowledge Base, 3 March 2026).
3. How big the shadow fleet is, by two different counts
The two headline counts do not agree, and the gap is wide enough that this page treats them as two separate, dated data points rather than a single number.
| Count | Ships | As of | Source |
|---|---|---|---|
| Ukraine's GUR war sanctions catalogue | 1,337 | February 2026 (cited April 2026) | Ukraine GUR, via shipfinex.com |
| Atlantic Council | about 1,140 | data basis August 2025 | Atlantic Council, 22 April 2026 |
| Same fleet, end of 2022 | about 600 | end-2022 | Ukraine GUR, via shipfinex.com |
| Broader "opaque market" count, active since Jan. 2021 | over 1,600 | November 2023 | Atlantic Council, 22 April 2026 |
| EU sanctions list | just under 600 | 18 December 2025 | gCaptain |
| OFAC-designated Iran-linked tankers (latest round) | 13 (e.g. AL SAFA, VETER, ZEVS) | 6 February 2026 | OFAC, US Treasury |
On volume rather than ship count, the Middle East Institute put the shadow fleet at roughly 18% of world tanker capacity and 6% to 7% of global crude flows in February 2026, a figure this page carries as a secondhand citation since it was only accessible via shipfinex.com, not the original report. Baltic Sea traffic adds another angle: Danish waters logged 292 transits by sanctioned ships and 122 vessel inspections over the course of 2025 (Atlantic Council, 22 April 2026).
4. Accident and environmental risk, and the visible traffic in AIS dark activity
Age and thin insurance combine into a specific kind of risk: if a 15-to-25-year-old tanker with no International Group P&I cover has an accident or spill, there is less, or no, insured capacity standing behind the clean-up and compensation. That is a structural consequence of the facts above, not a documented casualty count, and this page does not claim a specific spill or accident total for the shadow fleet because none was found with a date and source.
What is measured, and rising fast, is dark activity itself: Windward recorded 2,157 ships over 10,000 dwt with at least one AIS dark event in the second quarter of 2026, up 481% from 449 ships in the first quarter, while the number of dark events jumped from 451 to 3,137, up 595% (Windward, 11 August 2026). After the war broke out on 28 February 2026, visible AIS transits through Hormuz fell more than 83%, to just 450 in March against roughly 3,750 in February, the same report found. That is a different, escorted, kind of shipping, covered in our escorted convoy corridor entry. Oil sitting at sea for other reasons, including floating storage rather than sanctions evasion, is a separate topic, covered in our floating storage entry.
5. What this means for supply security, and for your buying timing
Soberly: the shadow fleet is one reason sanctioned oil keeps reaching the market at all, roughly 18% of tanker capacity by the Middle East Institute's figure, which means global supply is somewhat less tight than sanctions alone would suggest, but that flow is not a stable, guaranteed pipeline you can plan a purchase around. It runs on aging, thinly insured ships, unregistered AIS gaps and a sanctions list that keeps growing, 41 more EU-listed ships as of 18 December 2025 and 13 more OFAC-designated Iran-linked tankers as of 6 February 2026. Any of those, a seizure, an accident, a new sanctions round, can remove ships from the flow with no advance warning.
For a household or small business deciding when to buy heating oil or diesel, the practical takeaway is not to treat shadow fleet volumes as a floor under supply. Watch the dated, verifiable indicators instead, such as Brent and the actual tanker traffic through the Strait of Hormuz, and use our own numbers, not a hoped-for continuation of sanctioned flows, to time a purchase. Our heating oil: buy now or wait page sets out that decision logic in full.
See what today's fuel costs mean for your own household budget.
Run the calculator6. What the shadow fleet is not, and numbers often misused
The shadow fleet is not the same topic as the sanctions and price-cap regime built to constrain it; that trading and pricing mechanism is covered in full in our sanctions-shadow entry, and this page deliberately does not repeat its content. It is also not one agreed number: reports that cite a single figure, such as the 1,900-ship count from a widely shared blog post, could not be checked against a primary source with a clear date in our research and are not used here; only the 1,337 (Ukraine GUR, February 2026) and about 1,140 (Atlantic Council, August 2025) counts are, side by side.
It is also worth separating from a plain diesel supply squeeze, which has its own drivers and is covered in our diesel shortage entry. And while claims about Western oil majors knowingly benefiting from shadow fleet oil circulate widely, our research found no sourced, dated evidence for that specific claim, so this page does not make it.