The Strait of Hormuz has always imposed a choice: whoever controls its 33-kilometre narrows controls the oil beyond them. Nearly six months into the war between the United States and Iran, that choice has become literal. Ships transiting the waterway must now declare themselves for one of two rival corridors: an Iranian route hugging the northern coast near Larak and Qeshm islands, or a US-backed southern route off Oman. Most are choosing neither, and disappearing from tracking instead.
Shipping data from Kpler shows that between August 1 and August 19, 2026, a total of 236 vessels transited the strait. Of those, 83 openly used the Iranian northern route. Three used the Omani route. Two used the pre-war central corridor. The remaining 148, more than 60% of the total, went dark or used routes that could not be classified, according to Al Jazeera, citing Kpler.
The pattern is sharper among energy carriers. Of 112 vessels transporting crude oil, liquefied petroleum gas (LPG), or liquefied natural gas (LNG) in the same period, 21 declared the Iranian route and two declared the Omani. The remaining 89, over 80%, switched off their Automatic Identification System (AIS) transponders or transited by unverified means, the same data shows.
The scale of the collapse is itself striking. Before the war, approximately 138 ships passed through the strait each day, carrying roughly one-fifth of global oil supply, according to BBC analysis. By early March 2026, daily traffic had fallen around 95%, to an average of five or six vessels. By August 27, Kpler counted only five confirmed crossings in a single day, down from seven the day before. All five used the route Iran has designated for shipping, CNBC reported.
The war began on February 28, 2026, when the United States and Israel struck Iran. Iran responded by effectively closing the strait. The US Navy imposed a blockade, targeting ships it linked to Iran. Two rival passage systems have defined the waterway since: the Iranian route, which requires coordination with the Islamic Revolutionary Guard Corps (IRGC), and the Omani route, backed by the US and its allies. Navigating between them has proved both dangerous and commercially untenable.
Violence has reinforced that calculation. An oil tanker was struck by an unidentified projectile near the Omani coast on August 26. All crew were reported safe, and the United Kingdom Maritime Trade Operations (UKMTO) said an investigation was under way, according to CNBC. The week before, a separate attack on a cargo ship transiting the waterway killed a crew member. The identity of those responsible for either attack remains unknown.
The closure has not been continuous. On April 17, Iran's foreign minister said the strait was open. Within 24 hours, the IRGC declared it shut again, after two Indian-flagged ships came under fire during a transit attempt, according to the New York Times and Reuters. Around 20 vessels had attempted to exit the Gulf that evening; most turned back. Shipping groups including the Baltic and International Maritime Council (BIMCO) and Norway's Shipowners' Association raised unresolved concerns over mines and Iranian conditions, Reuters reported.
A preliminary US-Iran peace deal announced in June 2026 briefly raised hopes. It has since lapsed. Shortly after it was announced, only seven ships passed through Hormuz in four days, and more than 550 vessels remained stranded on either side of the strait. Iran later declared the waterway shut again. On a single Sunday in late June, total crossings dropped to 12, down from 35 the previous day, and five of eight vessels entering the strait had their AIS switched off, according to Al Jazeera, citing Windward data.
Iran and Oman have agreed on a temporary maritime corridor, but Iran's Deputy Foreign Minister Kazem Gharibabadi has said the waterway will not fully reopen until the US fulfils its commitments under the lapsed interim deal framework, CNBC reported. Peace talks are described as deadlocked. Donald Trump has said he has "no time schedule" for resuming negotiations.
US allies are sceptical that Iran's mines in the strait have been fully cleared, casting doubt on White House assurances that the waterway is safe, according to Bloomberg as cited by CNBC. Traffic at the Bab el-Mandeb strait, linking the Red Sea to the Gulf of Aden, has also slowed: 27 commodity vessels passed on August 20, down from 32 the day before, according to Reuters, citing Kpler.
What the data cannot show is where the dark ships actually go. Vessels with AIS switched off do not appear in commercial tracking counts, and figures from the US Central Command (CENTCOM) cannot be independently verified. The true daily transit total remains unknown. The majority going dark may be threading a path between two hostile powers, or finding ways around them. The data captures only the choice they are willing to make visible: to make no visible choice at all.
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