March 29, 2026: Iran War Maritime Intelligence Daily

At a Glance

• Transit through the Strait of Hormuz remains active but increasingly restricted, with six confirmed eastbound vessel movements under a tightly controlled Iranian corridor.
• Access is becoming less predictable, with multiple vessels denied passage, including two Chinese-owned ultra-large containerships.
• More than 50 containerships are now stranded west of the Strait, highlighting severe disruption to liner shipping.
• Bulk carriers, LPG tankers, and crude vessels continue to receive selective approval, reinforcing cargo-based prioritization.
• Vessels are being staged and sequenced for transit, with queue buildup indicating controlled throughput rather than recovery.
• A new U.S. MARAD advisory warns that AIS and onboard emissions are being used for targeting, increasing operational risk in the Red Sea and Gulf of Aden.
• Port activity continues to reflect rerouting pressure, with destination changes and transshipment volatility concentrated in the UAE and Oman.

Operational Overview 

Maritime activity in and around the Strait of Hormuz is entering a more restrictive and unpredictable phase. While vessel movement continues through the Iranian-managed corridor near Larak Island, access is no longer consistent or assured. Approval is increasingly conditional, opaque, and subject to shifting criteria.

The clearest signal of this shift is the denial of transit to two Hong Kong-flagged, Chinese-owned ultra-large containerships. These vessels were turned back after attempting to enter the corridor, indicating that even major international operators are not guaranteed access.

This is not an isolated case. Additional vessels, including bulk carriers, livestock carriers, and sanctioned tankers, have been delayed, denied, or left awaiting approval. At the same time, a limited number of bulk, tanker, and LPG vessels continue to move eastbound under the selective-access model.

Congestion west of Hormuz continues to build. More than 50 containerships are now stranded, while additional vessels are staging or repositioning for potential clearance. The corridor is no longer just controlling traffic — it is actively filtering it based on cargo type, ownership profile, and geopolitical alignment.

Beyond the Gulf, the risk environment is evolving. A new U.S. MARAD advisory highlights that AIS and onboard emissions are being used for targeting in the Red Sea and Gulf of Aden, reinforcing a shift toward reduced visibility and more defensive voyage management.

Strait of Hormuz Transit and Selective Denial

Transit through the Strait of Hormuz remained active on March 28, but access continues to be tightly filtered.

Six confirmed eastbound transits were recorded, consisting of three bulk carriers, one crude oil tanker, one LPG tanker, and one service vessel. This composition reflects the continued prioritization of agricultural cargo into Iran alongside outbound energy shipments.

Additional vessels were observed waiting, staging, or preparing to transit, reinforcing the presence of a controlled queue and sequenced passage through the corridor. While daily volumes remain limited, tracking shows that Iran has enabled up to a dozen vessels per day under this model, confirming that throughput is being actively managed.

At the same time, denial patterns are becoming more visible. A cargo vessel carrying food shipments to Pakistan remains awaiting approval after being turned back on March 24. A livestock carrier was also denied passage. A bulk carrier signaling China as its destination has been waiting since March 24. Another bulk carrier was observed approaching the corridor for potential transit.

The most significant development was the refusal of two ultra-large containerships (18,000+ TEU), owned by the Chinese state-controlled COSCO. These vessels were denied passage after approaching the IRGC-controlled corridor on March 27.

These ships are part of a major global alliance network that includes carriers such as CMA CGM and Evergreen, suggesting that network affiliation and prior port exposure may now influence approval decisions.

An additional Chinese-owned bulk carrier was also turned away, indicating that denial is not limited to container shipping and may reflect broader tightening of access criteria.

No containerships without direct links to Iran have transited since the Strait was effectively closed. With more than 50 container vessels now stranded west of Hormuz, liner shipping is facing disproportionate disruption compared to bulk and energy flows.

This confirms that the corridor is functioning as an active screening mechanism, where access is granted or denied based on cargo, ownership, and geopolitical alignment.

Vessel Access Pattern Through the Iranian Corridor

The structure of access remains visible in the types of vessels receiving approval.

Vessels linked to Pakistan, China, and Bangladesh continue to transit, particularly bulk carriers carrying agricultural cargo into and out of Iran. Tankers transporting Iranian energy commodities also remain among the primary beneficiaries of the system.

In contrast, vessels tied to global liner networks or with perceived links to the U.S., Israel, or their partners face increasing uncertainty. The denial of Chinese state-linked containerships, alongside earlier rejection of a Chinese-owned bulk carrier, indicates that approval is no longer predictable even for previously accepted profiles.

The corridor now operates less as a controlled reopening and more as a selective blockade. Normal commercial routing remains displaced, and access is governed through permissions, routing discipline, and partial AIS visibility.

Red Sea Signal Security and MARAD Advisory

A new U.S. MARAD advisory introduces a significant shift in how signal-based risk is treated in maritime operations.

The advisory warns that AIS transmissions and other onboard emissions may be used by hostile actors to locate and target vessels in the Red Sea and Gulf of Aden. U.S.-flagged vessels are now being advised to consider disabling AIS where it does not compromise navigational safety.

Additional risks include exposure through Wi-Fi networks, cargo telemetry systems, and weather reporting tools. Operators are advised to reduce emissions, vary routing and speed, and avoid predictable voyage patterns.

This reflects a fundamental change. AIS is no longer viewed only as a navigation and compliance tool — it is now recognized as a potential vulnerability in contested environments.

This guidance is likely to accelerate the normalization of semi-dark and dark activity across the Red Sea and adjacent regions.

Port Operations Disruptions

Port activity continues to reflect rerouting pressure and operational volatility across Gulf-adjacent hubs.

Inside the Gulf

Jebel Ali, UAE

• 4 transshipment rollovers (0-baseline from previous day, +75% vs 7-day average).
• 5 transshipment-delay cases (+66.67% from the previous day, −10.26% vs 7-day average).
• 4 transshipment-changed cases (+33.33% from the previous day, +250% vs 7-day average).

Ad Dammam, Saudi Arabia

• 8 transshipment rollovers (0-baseline from the previous day, 0-baseline vs 7-day average).

Jubail, Saudi Arabia

• 14 transshipment rollovers (0-baseline from the previous day, 0-baseline vs 7-day average).

Shuwaikh, Kuwait

• 4 transshipment-changed cases (+300% from the previous day, +600% vs 7-day average).

Outside the Gulf

Fujairah, UAE

• 22 port-of-destination changes (+46.67% from the previous day, +258.14% vs 7-day average).

Salalah, Oman

• 18 transshipment rollovers (+260% from the previous day, +3.28% vs 7-day average).
• 11 transshipment-delay cases (−52.17% from the previous day, −33.04% vs 7-day average).
• 4 port-of-destination changes (−55.56% from the previous day, −66.27% vs 7-day average).

Sohar, Oman

• 4 transshipment-delay cases (+300% from the previous day, +833.33% vs 7-day average).

These patterns show that rerouting pressure remains concentrated across the UAE and Oman, with dynamic destination changes and transshipment disruptions continuing at scale.

Outlook

The Strait of Hormuz remains open in function, but not in principle. Transit continues through a controlled Iranian corridor, where access is granted selectively and increasingly withheld without clear criteria. The denial of passage to large, globally integrated containerships signals a shift from managed flow to active filtering, where cargo type, ownership, and network exposure shape outcomes.

This is beginning to fragment global shipping behavior. Bulk and energy flows continue to move under defined conditions, while containerized trade faces disproportionate disruption, with vessels accumulating west of the Strait and limited alternatives available at scale.

At the same time, risk is extending beyond physical transit. The MARAD advisory formalizes a new layer of vulnerability, where AIS and onboard emissions are no longer neutral systems but potential targeting signals. This is likely to reinforce semi-dark operations across multiple theaters, not only in the Red Sea but across adjacent chokepoints.

The system is still functioning, but under tighter control, lower visibility, and increasing uncertainty. The key variable is no longer whether vessels can transit, but whether they will be permitted to — and under what conditions.