Strait of Hormuz 'Dark Fleet' Explained: AIS, Energy Tankers and India's Oil Security

Geography: The Strait of Hormuz is a narrow sea passage connecting the Persian Gulf to the Gulf of Oman and onward to the Arabian Sea. At its narrowest it is only about 33 km wide, with Iran to the north and Oman (the Musandam exclave) and the UAE to the south. Its shipping lanes are very narrow, leaving little room to manoeuvre.

Why it matters: Hormuz is the world's single most important oil chokepoint. In normal times, roughly one-fifth to one-quarter of the world's seaborne oil (about 20-21 million barrels per day) and about a fifth of global LNG pass through it. Because there is no full alternative route with matching capacity, even the threat of disruption sends shockwaves through global energy prices, freight and insurance costs.

The Automatic Identification System (AIS): AIS is a transponder system that continuously broadcasts a ship's identity, position, course and speed, mainly to avoid collisions and to allow tracking by authorities and other vessels. Under International Maritime Organization (IMO) rules (the SOLAS convention), AIS should normally remain switched on whenever a ship is sailing or at anchor — unless the master judges that broadcasting would threaten the ship's safety or security.

Going dark: To "go dark" is to switch off the AIS transponder (or spoof its signal), making the vessel untrackable and effectively invisible. While this can help a ship avoid detection, it significantly raises the risk of collisions — a danger that is acute in a congested chokepoint such as Hormuz.

The shadow/dark fleet: These overlapping terms describe a fleet of often ageing, opaquely-owned and inadequately-insured tankers used to move sanctioned oil (from Iran, Russia or Venezuela) while evading sanctions, price caps and mainstream insurance. Typical tactics include going dark, AIS spoofing, ship-to-ship transfers on the high seas, and frequent flag-hopping (re-registering under flags of convenience).

What is new: Historically this was a fringe practice tied to sanctioned cargoes. The novelty now is that, under wartime pressure at Hormuz, mainstream energy tankers — including those linked to Gulf national oil companies — are adopting the same evasive behaviour, pushing dark transits into the majority.

The 2026 Iran war (in brief): According to international reporting, the conflict began on 28 February 2026 with US and Israeli strikes on Iran, after which Iran moved to close the Strait of Hormuz to shipping. The United States then launched a campaign to reopen the strait and imposed a naval blockade of Iranian ports, while a conditional ceasefire has been in place at times. Through this period the strait has remained effectively closed or heavily contested, with traffic far below normal levels.

A fast-evolving, sensitive situation: This is an active and rapidly changing conflict, and details are contested across sources. For exam purposes the key takeaways are structural — the vulnerability of a single chokepoint, the impact on global energy markets, and the maritime-security dimension — rather than day-to-day military developments.

India's dependence: India imports the large majority of its crude oil, and a significant share of its energy transits Hormuz — over 40% of oil imports, around 60% of LNG and about 90% of LPG. This makes India structurally sensitive to any disruption at the strait.

India's response: India has steadily diversified its crude sources (now buying from around 40 countries), and the Petroleum Ministry has indicated that a large share of crude now arrives via routes outside Hormuz, supplemented by suppliers such as the US, Russia and West African producers. Other levers include the Strategic Petroleum Reserve (SPR), daily inter-ministerial monitoring of supply, assurances of adequate stocks of crude, LPG and LNG, and a longer-term push toward renewables and the energy transition to reduce import dependence. A distinction worth noting is between source diversification (buying from more countries) and route dependence (cargoes may still pass through the same chokepoint).

Safety and environment: With AIS off, vessels cannot be seen by others' systems, raising the danger of collisions, accidents and oil spills in one of the world's busiest waterways. Many such ships are also old and under-insured, magnifying the environmental and financial fallout of any incident.

Legal and security risks: Going dark sits in a legal grey zone under IMO rules and exposes operators to interception, seizure and enforcement action. The result is a maritime environment of reduced transparency, where commercial shipping continues only under elevated military and regulatory risk.

Global chokepoints: Hormuz is one of several critical maritime chokepoints alongside the Strait of Malacca (Asia-Pacific trade), the Bab-el-Mandeb and Suez Canal (Red Sea-Mediterranean), the Panama Canal, and the Cape of Good Hope (a longer bypass route). Disruption at any of them ripples through global trade.

Energy security as strategy: For India, the episode underlines energy security as a pillar of strategic autonomy — combining import diversification, strategic reserves, domestic production and refining, the clean-energy transition, and a credible naval presence and maritime-domain awareness in the Indian Ocean Region to safeguard sea lanes.

The crisis reinforces the case for India to deepen energy diversification and expand its Strategic Petroleum Reserve, while distinguishing source diversification from genuine route resilience. Accelerating the clean-energy transition — renewables, electric mobility, biofuels and efficiency — is the most durable way to cut exposure to oil-and-gas chokepoints over time. In the near term, strong maritime-domain awareness and naval reach in the Indian Ocean, coupled with diplomacy and strategic autonomy, can help protect Indian-bound shipping. Globally, the situation highlights the need to uphold freedom of navigation under the UN Convention on the Law of the Sea (UNCLOS), to de-escalate the conflict, and to address the safety and regulatory challenges posed by the spread of dark and shadow-fleet shipping.