Washington Hardens Hormuz Transit Rules for U.S.-Flag Ships
MARAD has issued a new U.S. maritime security advisory for the Persian Gulf, Strait of Hormuz, and Gulf of Oman that gives U.S.-flagged vessels more explicit operating instructions during transit. The advisory, numbered 2026-004 and effective March 13, 2026, tells U.S.-flagged ships that if they receive diversion orders or requests for voyage information from Iranian forces by email or VHF while those forces remain over the horizon, they should ignore those communications and continue passage if it is safe to do so, then immediately report the incident to NAVCENT Naval Cooperation and Guidance for Shipping. The notice also says vessels should maintain at least 30 nautical miles from U.S. warships, answer coalition navy calls, register with UKMTO before entering the reporting area, and expect continued GNSS disruption, including spoofing and jamming, across the region. To deal with that degraded navigation environment, mariners are specifically directed to rely more heavily on radar ranges, visual bearings, and cross-checking ECDIS information against secondary navigation sources rather than depending on satellite positioning alone.
Subscribe to the Ship Universe Weekly Newsletter
Click here for 30 second summary of the full piece ▶
MARAD just turned Hormuz transit advice into bridge-level operating rules
The new U.S. advisory tells U.S.-flagged ships to ignore Iranian diversion emails or VHF calls if safe to continue, update NAVCENT when such tactics occur, stay at least 30 nautical miles from U.S. warships, answer coalition naval calls, and expect continuing GNSS spoofing and jamming across the area. Mariners are specifically told to lean more on radar ranges, visual bearings, and secondary navigation checks rather than trusting GNSS alone.
- Key conduct order: do not comply with Iranian diversion instructions if safe passage can continue.
- Navigation warning: significant GNSS interference, spoofing, and jamming remain active across the operating area.
- Clear numeric rule: keep a minimum 30 nautical mile standoff from U.S. military vessels.
| Advisory bucket | Confirmed guidance | Operational threshold | Bridge and voyage-planning effect | Signals to watch next |
|---|---|---|---|---|
| Active advisory status |
MARAD Advisory 2026-004 is active and supersedes and cancels Advisory 2026-001 for the Persian Gulf, Strait of Hormuz, and Gulf of Oman.
The effective date is March 13, 2026, with automatic expiry on September 9, 2026 unless changed earlier.
Active U.S. guidance
|
Live now for U.S.-flagged vessels operating in the named waters. | Operators should treat this as the current baseline U.S. government transit rule set for the area, not as legacy regional advice. | Any update, replacement, or shortening of the advisory if the threat picture worsens or transit management becomes more formalized. |
| Diversion orders from Iranian forces |
If U.S.-flagged vessels are emailed or hailed on VHF by Iranian forces over the horizon and told to divert or provide voyage information, they are told to ignore the email or call and continue passage if safe to do so.
MARAD warns that following such directions may improve Iranian targeting accuracy.
Do not divert
|
Applies when safe continuation is possible. | Masters and company security teams now need a clear escalation script for suspicious diversion attempts, including immediate NAVCENT NCAGS updates. | More reports of over-the-horizon hails, scripted query patterns, and whether deceptive communications increase as traffic remains compressed. |
| GNSS interference |
The advisory states that significant GNSS interference, spoofing, and jamming continue across the area.
Mariners are told to increase reliance on radar ranges, visual bearings, and cross-checking ECDIS inputs with secondary navigation systems.
Degraded navigation environment
|
Persistent across the operating area, not a one-point anomaly. | This elevates the importance of manual cross-check routines, watchstanding discipline, and practical non-GNSS navigation competence during transit planning and execution. | Reports of spoofed positions, ECDIS misalignment, abnormal track jumps, and any operator move toward stricter bridge-team redundancy. |
| Distance from warships |
U.S.-flagged vessels should maintain a minimum standoff of 30 nautical miles from U.S. military vessels and answer all VHF calls from coalition navies.
The reason given is to reduce the risk of being mistaken for a threat while still supporting maritime awareness.
30 nm standoff
|
Minimum distance target whenever operating conditions allow. | Routing logic now has to balance security, traffic separation, warship proximity, and safe navigation at the same time. | Whether coalition transit management becomes more structured and whether informal vessel clustering around naval units is discouraged further. |
| Track selection and reporting |
MARAD advises staying as far as possible from Iran without compromising navigational safety, recommends transiting close to Oman when eastbound in the Strait of Hormuz, and directs vessels to register with UKMTO 24 hours before entering the Indian Ocean Voluntary Reporting Area.
Estimated times at Hormuz, Bab al-Mandeb, and or Suez are to be included in reports that auto-forward to NAVCENT NCAGS.
Tighter reporting discipline
|
Pre-voyage and en route reporting requirement intensifies before transit. | Voyage planning becomes more information-heavy, with higher emphasis on route discipline, ETA precision, and security communications. | Whether owners begin demanding more formal pre-transit bridge checklists and whether charter-party language shifts around war-risk route management. |
| Threat environment |
MARAD says Iranian threats now include direct missile attacks, armed UAVs, armed USVs, and historical boarding tactics using small boats and helicopters.
This is a wider threat envelope than classic detention or boarding guidance alone.
Multi-vector threat
|
High risk remains across the Persian Gulf, Strait of Hormuz, and Gulf of Oman. | Operators should read the advisory as a combined kinetic-threat and navigation-resilience document, not simply an anti-seizure advisory. | More missile or drone incidents, changes in traffic density, and any move by insurers or naval authorities to adjust operational assumptions. |
This tool is built for the operational logic behind the advisory. A ship does not become high risk because of one factor alone. The stress comes when deceptive communications, degraded navigation integrity, tight military operating patterns, and weak manual-navigation readiness stack on top of each other.
False or coercive instructions can become more dangerous when bridge teams are already overloaded or uncertain about who is controlling the maritime picture.
Spoofing and jamming are not abstract cyber issues here. They can distort position confidence right where precision matters most.
Getting too close to military units can create its own danger. Standoff discipline now becomes part of safe commercial behavior.
We welcome your feedback, suggestions, corrections, and ideas for enhancements. Please click here to get in touch.