MediumI Geo-Economics & Chokepoints28 September 2026, Monday

More than half of Hormuz transits now happen with transponders off

According to Windward, 24 ships crossed Hormuz on 27 September: 9 inbound and 15 outbound, with 14 transmitting no identification signal. A tracking page published the same day shows the latest IMF PortWatch record as a single transit on 20 September.

Location: HORMUZ

According to a daily summary from maritime tracking firm Windward dated 28 September, 24 ships passed through the Strait of Hormuz on 27 September. Of these, 9 entered the Gulf and 15 left it. Fourteen ships crossed dark, with the automatic identification system (AIS) that broadcasts their position switched off. Inbound ships included 5 tankers up to 333 metres long, and 11 of the 24 transits used the southern corridor.

The same summary relays a claim that more than 10 Fajr-5 rockets were fired on 27 September during a possible covert minelaying operation. Windward notes that this has not been verified and that traffic in the southern corridor did not fall. A satellite image from 26 September showed about 75 fast boats moving north in a single formation off Hasab. Since July the average had been 13.6 boats per image. Straits.live, meanwhile, gave the latest IMF PortWatch record on 28 September as 1 transit on 20 September. It puts the pre-crisis baseline at 85 transits a day. The gap between satellite detection and AIS-based counts shows that real traffic through the strait cannot be read from a single series.

Talay assessment

Bottom line

Traffic through the strait has not stopped entirely, but it is becoming increasingly invisible: 14 of the 24 transits on 27 September were dark. This suggests AIS-based counts understate the real flow through Hormuz. Part of the conflicting figures in the market may therefore stem from measurement method. The unverified mining claim and the concentration of fast boats raise the risks of dark transits.

Likely effects

Data reliabilityNegativeWeeks
A rising share of dark transits means official AIS-based series under-measure flows through the strait; pricing is splitting across different sources.
Maritime securityNegativeWeeks
The 75-boat formation and the unverified mining claim could lead insurers to keep their risk assessment for Hormuz transits tight.
Oil supplyUncertainWeeks
Continued tanker transits show the strait is not fully closed and that exports, however limited, are continuing via dark routes.

Possibilities, ranked

1
Dark traffic continues55%
Transits stay in the tens per day and the dark share remains high; official series keep understating the flow.
Watch: The dark transit ratio in Windward's daily summary
2
Security incident30%
The mining claim is confirmed or fast boats intercept a ship; traffic in the southern corridor falls.
Watch: Southern corridor transit counts and UKMTO warnings
3
Visible recovery15%
A diplomatic step leads ships to cross with AIS switched on, and visible transits rise markedly.
Watch: AIS-on transits rising above 24 ships

Probabilities are calibrated judgement based on the sources, not measurement, and are revised as new information arrives. Not investment advice.

Market reaction

Indicators affected

Hormuz transits, 27 September (Windward)▲ 24 ships
Dark transits▲ 14 ships
Pre-crisis daily baseline▼ 85 transits

Historical context