AIS Switch Off and Ship-to-Ship Transfers: 7 Vital Rules for Seafarers in 2026
If you have stood a bridge watch on a tanker in the last two years, you have probably seen it: a target on the radar with no AIS label, sitting close to another ship far from any port. The AIS switch off and the quiet ship-to-ship (STS) transfer are now the two main tools of the “dark fleet”. For crews, this is not just a news story. It can affect your safety, your insurance cover and even your freedom.
This guide explains, in simple terms, when an AIS switch off is legal, what a proper STS transfer looks like, and seven practical rules to protect yourself in 2026.
Why AIS Switch Off and Ship-to-Ship Transfers Matter in 2026
Under SOLAS Chapter V, Regulation 19, ships of 300 GT and above on international voyages must carry AIS and keep it working. AIS helps prevent collisions, supports search and rescue, and lets coastal states see who is in their waters.
Dark activity, mostly a deliberate AIS switch off, has grown sharply this year. Analytics firm Windward reported that the number of large cargo ships and tankers with at least one AIS gap of three days or more jumped from 449 in the first quarter of 2026 to 2,157 in the second quarter. Much of this is linked to sanctions evasion, the Gulf conflict and AIS spoofing, where a ship transmits a false position.
Many of these ships then meet another vessel at sea and move cargo in an STS transfer, so the origin of the oil is hidden. If you want to understand the wider picture, read our guide to dark fleet tankers and their warning signs.
When Is an AIS Switch Off Allowed?
The key rule is in the IMO guidelines on the onboard use of AIS, IMO Resolution A.1106(29). It says AIS should always be in operation when a ship is underway or at anchor. There is only one exception: the master may switch it off if he or she believes that keeping it on could compromise the safety or security of the ship, for example in a piracy area.
Conditions for a legal AIS switch off
- The decision belongs to the master, using professional judgement, not to the charterer or an office instruction to “go dark” for commercial reasons.
- There must be a real safety or security reason, such as a piracy or armed attack threat.
- The action and the reason must be recorded in the ship’s logbook.
- If the ship is in a mandatory reporting system, the master should inform the authority, unless this itself creates danger.
- AIS must be switched back on as soon as the danger has passed.
In war-risk areas like the Strait of Hormuz, some legitimate ships have gone dark with the agreement of owners and flag. That kind of AIS switch off is very different from a tanker that disappears for days only to reappear fully loaded. See our article on Strait of Hormuz shipping risks for more on transits in that area.
What a Legitimate STS Transfer Looks Like
STS transfers are a normal and legal part of tanker trading. Lightering big crude carriers, topping up cargo and bunkering at sea all happen every day. For oil tankers of 150 GT and above, MARPOL Annex I Chapter 8 requires an approved STS operations plan on board, and the coastal state must be notified in advance (normally at least 48 hours) when the transfer takes place in its territorial sea or exclusive economic zone.
A proper STS transfer usually has a named, approved location, a mooring master or STS superintendent, fenders and hoses checked and certified, and a clear communication plan between the two ships. Both vessels keep AIS on throughout.
Red flags during an STS transfer
- The other ship has no AIS signal, a different name on the hull from its AIS data, or a freshly painted name.
- You are told not to record the transfer in the oil record book or deck log.
- The location is in open sea, far from any declared STS area, at night with lights reduced.
- Cargo documents are missing, changed or prepared after the operation.
- The company asks crew not to take photos or to delete messages.
The Risks for Crew
In December 2023 the IMO Assembly adopted a resolution urging flag and port states to act against illegal “dark fleet” operations. Port states were asked to report ships that deliberately avoid detection, for example by turning off AIS or LRIT, and to watch STS operations in their waters more closely.
For seafarers, this means more boarding, detention and investigation. P&I clubs have also warned that an AIS switch off outside the IMO guidelines can breach SOLAS and may let the insurer refuse cover. Maritime Mutual describes such cloaking as a deceptive shipping practice in its AIS cloaking risk bulletin. If cover goes, so may your safety net if something goes wrong, including medical costs, repatriation and wages if the ship is abandoned.
Officers who carry out an unlawful AIS switch off can also be named in sanctions or criminal cases. Our guide on war zone rights for seafarers explains what support you can ask for when the voyage becomes dangerous.
7 Rules to Protect Yourself on Watch
1. Treat every AIS switch off as a logged event
Make sure the time, position, reason and the master’s order are written in the deck log. If it is not written down, it did not happen, and you may carry the blame later.
2. Check AIS status at every watch handover
Confirm there has been no AIS switch off, that the unit is transmitting, and that the static data (name, IMO number, destination, draught) is correct. Wrong or false data is as serious as switching it off.
3. Ask for the STS plan and notifications
Before any STS transfer, ask to see the approved plan, the location and the notice sent to the coastal state. A professional company will have these ready.
4. Keep your own simple notes
Note dates, positions and instructions in a personal notebook. Do not take secret recordings or break company rules, but keep a factual record.
5. Use the right reporting channels
If you feel pressured, contact the Designated Person Ashore (DPA). If that fails, contact your flag state, union or the ITF.
6. Check your ship before you sign on
Look up the vessel’s flag, age, owner and P&I club. A very old tanker with an unknown insurer and a recently changed flag should make you ask questions.
7. Know your MLC rights
Under MLC 2006, you have the right to a valid contract, repatriation and financial security against abandonment. Keep copies of your contract and wage slips.
FAQ
Can the master legally order an AIS switch off?
Yes. An AIS switch off is allowed only when keeping AIS on would put the ship’s safety or security at risk, such as a piracy threat. The reason must be logged and AIS restarted as soon as the danger passes.
Are ship-to-ship transfers illegal?
No. STS transfers are legal when done in approved areas, with an STS plan, proper equipment and notice to the coastal state. They become a problem when used to hide cargo origin or avoid sanctions.
What should I do if I am asked to falsify records?
Do not falsify the log or oil record book. Raise it with the master and DPA, keep your own factual notes, and contact your flag state, union or the ITF if the pressure continues.
Conclusion
AIS and honest STS operations are there to keep ships, crews and the sea safe. An AIS switch off has a narrow, legal use, and anything outside it can put your career and insurance cover at risk. Know the rules, log everything, and speak up early. The safest ship is one that has nothing to hide.
Disclaimer: This article is for general information and guidance only, and some of the information may now be out of date. Any information about rules and regulations (for example from the IMO, ILO, flag states, DG Shipping/DGMA or other maritime authorities) should be checked on the official website of the authority concerned for its current applicability before making any decision. CrewMirror and its owners and operators will not be responsible for any loss or damage caused by the use of information published on CrewMirror pages and posts.
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