Over half of Hormuz tanker crossings now occur in the dark, with hidden movements reaching 57% of all tracked transits, Vortexa strategists said in a Friday note.
Since March 1, vessels have switched off AIS signals during hundreds of Strait of Hormuz crossings, pushing dark movements to 57% of all recorded transits and limiting visibility into cargo flow.
After accounting for 58.5% of outbound laden transits in March, dark voyages eased to 54% in April when traffic volumes surged, before jumping to 65.2% in May, Vortexa said.
Non-Iranian operators now account for most dark outbound laden voyages through Hormuz as shipping companies increasingly switch off AIS signals to manage conflict risks and operational uncertainty while keeping Gulf cargoes moving.
Outside Hormuz, dark loading activity accelerated sharply between April and May, indicating that reduced transparency now extends beyond transit movements alone, according to Vortexa.
Where dark loadings initially centered on Das Island, Zirku and Jebel Dhanna terminals, activity later expanded toward Fujairah terminal and nearby ship-to-ship transfers, Vortexa added.
Despite strong export volumes from the UAE throughout the crisis, the share of cargoes loaded under dark conditions climbed from minimal levels in early March to above 90% recently.
Across April and May, Very Large Crude Carrier vessels consistently handled about 59% of dark cargo loadings, underscoring operators' focus on moving larger parcels despite disruptions, the note added.
Crude oil and condensates accounted for about 40% of dark outbound laden movements through Hormuz, while clean products accounted for nearly 25%, dirty products for close to 18%, and liquefied petroleum gas for around 14%.
Reduced AIS visibility is making fuel flows harder to track beyond crude oil, while VLCC vessels account for roughly 25% to 33% of dark outbound transits each month, Vortexa said.
Non-Iranian operators increased their share of dark outbound laden transits through Hormuz from 37% in March to 56% in April and 67% in May, showing that AIS-off navigation is becoming more widely used across the Gulf, the note added.
UAE-linked vessels account for about 27% of non-Iranian dark movements, followed by Iraq at 11% and Qatar at 10%, while Saudi Arabia, Kuwait and Bahrain contribute another 9%, indicating that dark transits can no longer be viewed mainly as Iranian-linked activity.
Growing use of dark shipping is making Gulf energy exports harder to track, increasing uncertainty around cargo origins, delivery timing and supply availability across crude oil, fuels, LPG and LNG markets, according to Vortexa.