Shadow fleet navigates Strait of Hormuz amid US blockade and sanctions
Probe shows shadow fleet using false flags and disabled AIS to cross the Strait of Hormuz during a US naval blockade, aided by shell companies now exposed.
A shadow fleet moved through the Strait of Hormuz during intense military operations and a subsequent US naval blockade, an open-source probe has found. The investigation tracked hundreds of voyages between March 1 and April 15 and found vessels using fake flags, disabled AIS and opaque ownership to skirt restrictions. The March 11 strike on the Thai cargo ship Mayuree Naree, which left three crew dead after a fire and grounding off Qeshm island, underscored the human cost as covert trade continued.
Attack on Mayuree Naree and the human toll
On March 11 the Thai-flagged Mayuree Naree was hit by two projectiles while transiting the Strait of Hormuz, sparking an engine-room fire. Rescuers saved 20 sailors but three crew members remained trapped; their remains were located weeks later when specialists boarded the grounded vessel off Iran’s Qeshm island. The strike and its aftermath heightened fear among mariners and drew international attention to the risks facing commercial traffic in the choke point.
Voyage monitoring recorded 202 crossings
Investigators monitored 202 voyages made by 185 distinct vessels through the strait between March 1 and April 15. Of those transits, 77 voyages — roughly 38.5 percent — were directly or indirectly linked to Iran, and 61 vessels were listed on international sanctions registers. The tracking effort cross-referenced IMO numbers with sanction lists and AIS data to map movements amid conflict and interdiction attempts.
Three phases of passage during the crisis
Analysts divided the period into three operational phases. Phase 1, described as open war (March 1–April 6), saw 126 transits with a peak day of 30 vessels and 46 links to Iranian entities. Phase 2, a fragile truce (April 7–13), recorded 49 crossings, more than 40 percent tied to Iran and including sanctioned, Iranian-flagged vessels that successfully left the Gulf. Phase 3 followed the US-imposed blockade beginning April 13; despite the blockade, 25 ships still crossed the strait between April 13 and April 15.
Tactics: disabled AIS, fake flags and shell companies
The shadow fleet used multiple tactics to mask identity and destination, frequently manipulating Automatic Identification System transmitters by disabling or jamming signals. Investigators identified at least 16 ships operating under false flags, including registries from unexpected jurisdictions such as Botswana, San Marino, Madagascar, Guinea, Haiti and Comoros. Ownership chains were obscured through shell companies, and nearly 19 percent of operators remained unidentifiable from open records.
Operators and routes that skirt enforcement
Commercial managers for the vessels were spread across a global network, with a notable share based in Iran (15.7 percent), China (13 percent), Greece (more than 11 percent) and the United Arab Emirates (9.7 percent). Smaller coastal vessels without IMO numbers, such as a vessel identified as “13448,” were able to evade some monitoring tools and completed voyages from Iran to Karachi. Other ships, including Panama-flagged units like the Manali, pierced the cordon and continued toward destinations such as Mumbai.
Energy cargoes and continuing commercial flows
Energy shipments remained a substantial component of traffic through the strait despite the fighting and blockade. Sixty-eight vessels — about 36.2 percent of the tracked traffic — were carrying crude oil, petroleum products or gas, with ten tankers directly linked to Iran. Non-oil maritime commerce also persisted, with dozens of bulk and general cargo ships recorded during the open war phase, many tied to Tehran. The sustained movement highlights how trade networks adapt even under acute geopolitical pressure.
The continuing flows have produced broader disruptions: pre-conflict averages of around 100 ships daily through the strait collapsed, and maritime authorities report thousands of seafarers and hundreds of ships effectively immobilised across the Gulf region. The International Maritime Organization described the situation as unprecedented in modern times, with an acute strain on crew welfare, insurance markets and port operations.
The probe’s findings show a parallel maritime system operating alongside formal trade routes, formed in part by decades of sanctions, complex ownership structures and technical measures to conceal movements. That system proved resilient in the face of a declared naval blockade, revealing practical gaps in enforcement and the limits of interdiction when adversaries can exploit legal, technical and commercial loopholes.
As regional authorities and international partners weigh responses, the immediate challenges are protecting merchant crews, restoring safe navigation and improving the transparency of vessel registries and tracking. Longer-term measures will likely include tighter flag-state oversight, enhanced AIS anomaly detection and stronger cooperation on corporate transparency to prevent the use of shell companies and false flags.
The sea lanes of the Gulf remain a strategic artery for global energy and commerce, and the exposure of a shadow fleet operating through the Strait of Hormuz underscores how security, law and commerce intersect in times of conflict. Continued monitoring and coordinated international action will be necessary to reduce risk to mariners and to close avenues that allow sanctioned or illicit shipments to move through the region.
