Ships go dark in Strait of Hormuz after US-Iran escalation

A growing number of vessels are switching off their tracking systems while passing through the Strait of Hormuz, as heightened military tensions between the United States and Iran disrupt one of the world's most critical shipping lanes, Bloomberg reports.

According to preliminary Kpler data, all six commodity carriers that transited the Strait of Hormuz on Sunday did so with their Automatic Identification System (AIS) transponders turned off. So-called "dark crossings" have outnumbered observable transits over the past three days.

Ship-tracking data based on AIS signals showed no vessels visibly passing through the strait early Monday. However, several ships appeared on opposite sides of the waterway—in either the Persian Gulf or the Gulf of Oman—after last broadcasting their positions from the other side, indicating they had crossed Hormuz without transmitting their locations.

The increase in secret crossings comes as Washington and Tehran exchange retaliatory attacks while issuing conflicting statements over control of the strategic waterway.

Observable transits along the US-supported southern shipping corridor off the Omani coast have come to a complete halt, with the last recorded passage occurring on July 8. By contrast, the northern route, designated by Iran as a safe passage, continued to handle a limited number of crossings through July 11.

Recent Iranian attacks on vessels using the Omani corridor—including some operating with their transponders switched off—appear to have discouraged traffic along that route. Shipowners opting for the northern passage, however, face potential costs imposed by Iran as well as the risk of US penalties.

Secret transits through the Strait of Hormuz first became widespread in mid-April, when the United Arab Emirates began exporting oil from the Persian Gulf aboard tankers operating without active AIS signals. The move partially mitigated the oil supply disruptions that had been widely anticipated during the early stages of the conflict.

Iran and the United States also offered competing accounts over the weekend regarding navigation through the strait. Tehran stated that ships would only be permitted to transit Hormuz after obtaining authorization from an Iranian entity, while US Central Command maintained that "there are still pathways open to ships looking to cross freely."

Iranian forces have attacked four vessels over the past seven days, with all incidents occurring on the northeastern side of Oman's Musandam Peninsula. The locations suggest the ships were using the US-backed shipping corridor along the Omani coast.

The Islamic Revolutionary Guard Corps (IRGC) said on Sunday night that it had intercepted two vessels it claimed were endangering maritime traffic by traveling along an "illegal route."

By Vafa Guliyeva