Windward, the maritime analytics firm, identified 92 AIS denial zones and 44 GPS jamming zones across The Persian Gulf on 5 March — 136 areas where the electronic systems that keep commercial shipping safe have been deliberately disabled.
The Automatic Identification System is mandated by the International Maritime Organisation under the SOLAS convention for all vessels over 300 gross tonnes on international voyages. It broadcasts vessel identity, position, course, and speed to other ships and shore-based traffic management. GPS provides the positional data that feeds AIS and underpins all modern navigation. In the strait of Hormuz — roughly 21 nautical miles wide at its narrowest, with designated shipping lanes only two miles wide in each direction — loss of either system creates immediate collision and grounding risks. Approximately 20,000 seafarers and 15,000 cruise passengers remain stranded in these waters, unable to navigate safely out of the area even if insurance and military conditions permitted transit.
The jamming introduces a specific problem for the one arrangement that has produced a physical transit result. China's separate Hormuz passage arrangement relies on vessels broadcasting Chinese ownership credentials via AIS — the vessel referred to as Iron Maiden completed its transit precisely this way. AIS denial zones make that identification mechanism unreliable. If Iranian electronic warfare cannot distinguish a Chinese-flagged tanker from a Western-flagged one inside a denial zone, the safe passage arrangement depends on coordination that the electronic warfare environment actively undermines. Iran's own remaining naval assets lose the ability to identify friendly traffic in the fog its own forces have created.
Iran has demonstrated electronic navigation denial capabilities before — Iranian officials attributed the 2011 capture of a US RQ-170 Sentinel drone to GPS spoofing, and Iran has deployed electronic warfare systems along its Gulf coast for over a decade. The 136 denial zones Windward documented represent a systematic blanketing of Gulf waters, adding a layer of physical navigational danger on top of the insurance withdrawal that has already halted commercial traffic. Each compounding layer raises the threshold for resumption of shipping. Even a ceasefire would not immediately restore safe navigation; electronic warfare infrastructure would need to be stood down, zones verified clear, and insurers convinced — a process measured in weeks, not hours.
