Every U.S. maritime advisory for the Strait of Hormuz carries a printed expiry date. When one lapses, it is not the end of the guidance, but the start of the next revision, and the security specifics can shift with each one. 

For a master planning a transit, the practical question is which parts of the current advisory change when the number rolls over, and which parts hold regardless of what any document says. The answer separates temporary security instruction from standing seamanship.

How the U.S. Maritime Advisory System Works for Hormuz

U.S. maritime advisories for the Gulf are a rolling series, each superseding the last. Advisory 2026-004, covering the Persian Gulf, the Strait of Hormuz, and the Gulf of Oman, was issued in March 2026 with an automatic expiry printed into it. Advisory 2026-011 has since superseded and cancelled it, continuing the coverage.

That rollover is the normal mechanism, not a lapse in protection. When an advisory reaches its expiry date, the U.S. Maritime Administration either lets it stand until replaced or issues a new number that supersedes it. For a bridge team, the takeaway is procedural: always work from the current advisory, confirmed on the MARAD Maritime Security Communications with Industry portal, rather than a copy saved weeks earlier. The number changes; the requirement to hold the latest one does not.

What the Current Advisory Requires

Read as a whole, the advisory is a security document, and its security measures are tied to the threat picture at the time of issue. The core instructions in the 2026 series include:

• Keep at least 30 nautical miles clear of U.S. naval vessels to avoid misidentification.

• Ignore over-the-horizon VHF or email instructions from Iranian forces to divert or submit voyage information, and continue passage if safe to do so.

• Log any such encounter and report it to Naval Forces Central Command NCAGS.

• Coordinate with NCAGS and review UKMTO and Joint Maritime Information Center advisories before, during, and after transit.

Those measures are the elements most likely to be revised as the situation changes. The standoff distance, the reporting contacts, and the threat description belong to the current advisory and should be read fresh from it each voyage.

The Navigation Guidance That Carries Forward

One paragraph in the series is not a security instruction at all. Both Advisory 2026-004 and its successor 2026-011 carry the same navigation guidance: significant GNSS interference, spoofing, and jamming continue across these areas, and given the degraded positional integrity environment, mariners should increase reliance on traditional navigation methods including radar ranges, visual bearings, and cross-checking ECDIS inputs with secondary navigation systems.

That paragraph did not expire when 2026-004 did. The guidance carried straight into the replacement, because it describes navigation practice rather than a security posture. Radar ranges, visual bearings, and a position cross-checked against something other than the satellite are not tied to a flag, a threat actor, or a calendar. Each is what a bridge does when the electronic position cannot be trusted, and that is a permanent condition in these waters, not a temporary one.

Traffic Has Fallen, but the Waterway Has Not Closed

The operating environment reflects how seriously operators treat the risk. No formal legal closure of the Strait of Hormuz has been declared, and passage remains legally permissible, yet many operators have chosen to wait. Joint Maritime Information Center monitoring recorded daily transits falling to a fraction of the historical average of roughly 138 vessels per day, with some days in early 2026 seeing only a handful of transits.

That reduction is a function of operator decisions rather than any promulgated closure. For vessels that do transit, congestion at anchorages and clustering around Fujairah, Khor Fakkan, and the eastern approaches add routine navigation risk on top of the interference and the security threat. A degraded positional picture in crowded water is exactly the situation the navigation paragraph is written for.

What a Bridge Team Should Do

Preparing for a Hormuz transit means treating GNSS as unreliable from the outset. The 2026 industry guidance for the strait, supported by major shipping bodies, sets the planning assumption as total unavailability or unreliability of the GNSS signal for the entire transit. From that, the practical measures a bridge can apply are:

• Fix the position manually at a written interval, with guidance recommending every six minutes or less near hazards.

• Maintain continuous dead reckoning so an independent position is always running.

• Optimize radar with split ranges and use parallel indexing against charted features.

• Keep the autopilot in heading mode and disengage GNSS-based track control.

• Run a GNSS-loss drill before entering the area, reviewed by the master and the company DPA.

• Carry corrected paper charts as backup for terrestrial position plotting, and confirm officers are proficient in plotting by hand.

None of these depend on the advisory being current, or on any advisory existing at all.

The Guidance With No Expiry Date

A U.S. advisory tells a master what the threat looks like this month. The navigation paragraph inside it describes what to do when the satellite lies, and that has no expiry date. Working from the current advisory, keeping GNSS readiness continuous, and carrying a corrected chart folio are what protect a transit, whichever number is in force. For corrected charts, IMO and SOLAS publications, and navigation resources, contact American Nautical Services at +1 (954) 522-3321 or sales@amnautical.com.

Frequently Asked Questions

Here are answers to common questions about Strait of Hormuz transit guidance.

Q. What happens when a U.S. maritime advisory expires?

U.S. advisories carry a printed expiry date and are part of a rolling series. When one expires, it is either left to stand until replaced or superseded by a new numbered advisory. Advisory 2026-004 was superseded by 2026-011, which carried the guidance forward. Masters should always work from the current advisory.

Q. Is the Strait of Hormuz closed to shipping?

No. No formal legal closure has been declared, and passage remains legally permissible. However, many operators have chosen to reduce or suspend transits, and daily traffic has fallen well below the historical average of around 138 vessels per day as a result of those decisions.

Q. What navigation guidance applies in the Strait of Hormuz?

Because of significant GNSS interference, spoofing, and jamming, mariners are advised to increase reliance on traditional methods: radar ranges, visual bearings, and cross-checking ECDIS against secondary navigation systems. Industry guidance sets the planning assumption as total GNSS unavailability for the entire transit.

Q. How far should vessels stay from U.S. naval ships in the Gulf?

The 2026 U.S. advisories instruct commercial vessels to keep at least 30 nautical miles clear of U.S. naval vessels to avoid misidentification. Vessels should also coordinate with NAVCENT NCAGS and monitor UKMTO and JMIC advisories.

Q. Should a vessel follow VHF instructions from Iranian forces?

U.S. advisories instruct vessels not to comply with over-the-horizon VHF or email instructions from Iranian forces to divert or submit voyage information, and to continue passage if safe to do so. Any such encounter should be logged and reported to NCAGS.

Q. Do I need paper charts to transit the Strait of Hormuz?

Industry guidance recommends carrying up-to-date paper charts as a backup for terrestrial position plotting, particularly given the assumption that GNSS will be unavailable. Officers should be proficient in plotting position by hand, since the electronic position cannot be relied upon during the transit.