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AIS, sanctions and the shadow fleet

The ships on the globe on the analysis page come from AIS signals. Here is how the system works, what it can and cannot tell you, and how it is used when authorities and analysts follow sanctioned oil trade.

Updated · about 4 min read · Written by OESA

What AIS is

AIS (Automatic Identification System) is a radio system in which ships automatically transmit their identity, type, position, course, speed, navigational status and other safety information to other ships and to shore stations. It was designed to prevent collisions and for traffic monitoring, not to track ships worldwide.

Under the SOLAS convention (chapter V, regulation 19), AIS must be carried by all ships of 300 gross tonnage and upwards on international voyages, cargo ships of 500 gross tonnage and upwards not on international voyages, and all passenger ships. The requirement applied to all ships from 31 December 2004. AIS must be kept on at all times, except where international rules provide for the protection of navigational information (IMO).

Ships under the requirement use Class A. Smaller vessels, such as fishing and leisure boats, often use Class B, which transmits less often.

What the messages contain

  • Static data: MMSI number, IMO number, name, call sign, ship type and dimensions.
  • Movement: position from satellite navigation, course, speed and status (for example at anchor or under way). Sent automatically.
  • Voyage data: draught, destination and expected arrival. Entered by hand by the crew and often outdated or wrong.

The MMSI is the ship's radio number, nine digits. The first three digits (MID) show the country that issued the number, which is usually the flag (ITU). The IMO number has seven digits, stays with the ship for life and does not change when the ship gets a new flag, owner or name (IMO). That is why sanctions lists use the IMO number.

How ships are tracked: shore and satellite

  • Shore-based receivers pick up signals from ships within VHF radio range, which in practice means along the coast.
  • Satellites pick up signals far from land. Norway has its own AIS satellites (NorSat), used by the Norwegian Coastal Administration. Where there are very many ships, messages can collide and the satellite misses some of them.
  • Data providers combine signals from many sources. OESA uses the Norwegian Coastal Administration (Norwegian waters), Fintraffic/Digitraffic (the Baltic) and aisstream.io (shore-based receivers elsewhere), and shows a selection of ships: tankers, LNG carriers, offshore vessels and Russian-flagged ships.

What AIS does not tell you

  • Coverage gaps. A ship that is not shown is not necessarily absent. It may be out of range.
  • Switched-off transmitters. A ship can turn AIS off, sometimes for legitimate safety reasons, for example in waters with piracy, and sometimes to hide where it is.
  • False data (spoofing): a ship can transmit a false position or another identity.
  • Errors in the manual fields, such as destination and draught.
  • The flag derived from the MMSI number can be wrong or outdated.

That is why analysts combine AIS with satellite imagery, port data and ownership data. Flag states also have LRIT (Long-Range Identification and Tracking), a separate satellite system for position reports that is not open to everyone.

Sanctions against ships

Sanctions lists name people and companies, but also individual ships, identified by their IMO number. The main lists for ships are:

  • United States: OFAC's Specially Designated Nationals (SDN) list.
  • United Kingdom: the UK Sanctions List.
  • EU: ships banned from EU ports and from buying services there, listed in an annex to the Russia sanctions regulation.

The price cap on Russian crude oil was introduced in December 2022 by the G7, the EU and Australia. Companies in these countries may only provide services such as insurance, finance and shipping if the oil was bought at or below the cap. The cap was USD 60 per barrel when it was introduced (US Treasury). The level has since been adjusted and is not necessarily the same in every country; check the official sources for what applies now.

The shadow fleet

The International Maritime Organization (IMO) describes the “shadow fleet” or “dark fleet” as ships engaged in illegal operations to circumvent sanctions, evade safety or environmental rules or avoid insurance costs (resolution A.1192(33), December 2023).

The countries behind the price cap have described its typical features (Price Cap Coalition, October 2024):

  • older ships with opaque ownership, often through companies that own a single ship,
  • insurance from unknown or thinly capitalised providers,
  • classification outside the established classification societies and flags from states that do not meet their obligations,
  • AIS that is switched off or manipulated,
  • ship-to-ship transfers on the open sea to hide where the cargo comes from.

No single feature proves anything. Ship-to-ship transfers are common and legal in many settings, and old ships are not illegal. The risk the authorities point to is accidents and oil spills that nobody can pay for.

Using the globe

  • The “Ships from AIS” layer is on by default on the globe. Click a ship for its name, type, speed, flag and how old the position is.
  • The “Only Russian and sanctioned ships” layer shows ships with a Russian flag (derived from the MMSI number) and ships whose IMO number is on OFAC's or the UK's list.
  • A match means the ship is on a list, not that it is doing anything illegal on this particular voyage. And ships outside coverage are not shown.

Sources

The guides are written by OESA students to explain concepts and how things fit together. They are not investment advice. Figures that are not definitions carry a source and a date; if you find an error, let us know at styret@oesa.no.

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