Quarter of Large Oil Tankers Escape Iran War, 29 Vessels Cross Hormuz

Roughly one‑quarter of the super‑tankers that were trapped in the Persian Gulf when the Iran‑U.S. war erupted on Feb. 28 have managed to exit the waterway, according to Bloomberg‑compiled shipping data [1]. Twenty‑nine of the 109 vessels capable of carrying 700,000 barrels or more have now traversed the Strait of Hormuz, albeit in a slow and often covert manner [1].

Key takeaways

• 29 of 109 large tankers (≈25%) have crossed the strait since the war began [1]
• Transits have been conducted at night and often with AIS “dark” to avoid rocket threats [1]
• The escaped cargoes amount to about 520,000 barrels per day, a small slice of the oil still locked in the Gulf [1]
• Iran‑linked ships were excluded from the count because they enjoyed free passage until mid‑April [1]
• Global oil inventories are falling at a record pace, intensifying market pressure [3]

Stealthy Crossings Amid Ongoing Hostilities

The vessels that have succeeded in leaving the Gulf did so under challenging conditions. Many opted to sail under cover of darkness to reduce exposure to shore‑based rocket fire, and a significant number switched off their Automatic Identification System (AIS) signals, a practice known as “going dark,” which complicates tracking efforts [1]. Some governments reportedly lobbied on behalf of cargo owners to secure permission for the risky passages. Iran‑linked ships were not included in the tally because they were allowed free movement through Hormuz until mid‑April, after which they too faced restrictions [1].

Despite the limited number of transits, the escaped oil—estimated at roughly 520,000 barrels per day—has helped alleviate some pressure on a global market already strained by shrinking inventory buffers [1]. However, the overall volume remains a fraction of the crude and refined products still stranded in the Gulf, and analysts note that the true number of escaped vessels could be higher due to the prevalence of “dark” ships that do not broadcast their positions [1].

Broader Market Context and Future Outlook

The war’s impact extends beyond tanker movements. The International Energy Agency reported that global oil stockpiles were drawn down at a record rate of about 4 million barrels per day in April, as the Hormuz closure choked supply and forced markets to tap backup reserves [3]. Cumulative inventory losses since February exceed 1 billion barrels, underscoring the severity of the supply shock [3]. Meanwhile, the U.S. Treasury announced a 30‑day extension for countries to import Russian oil already in tankers, a move aimed at mitigating shortages caused by the Iran conflict [2].

Why it matters

The gradual exodus of large tankers signals a modest easing of the logistical bottleneck that has constrained oil flow since the war began. Each successful crossing frees up vessel capacity that could be redeployed once a durable cease‑fire is secured, potentially restoring a larger share of the roughly one‑fifth of world oil that normally moves through Hormuz. Nonetheless, with global inventories dwindling and many ships still “dark,” the risk of renewed supply constraints remains high. Continued diplomatic progress between the United States and Iran will be crucial to expanding traffic through the strait and stabilizing the market.