The US has issued a new advisory to U.S.-flagged commercial vessels transiting the Red Sea, Bab el Mandeb Strait, Gulf of Aden, Arabian Sea, and Somali Basin with Automatic Identification System (AIS) transponders on as they are at increased risk of being targeted by Houthis.

The U.S. Department of Transportation’s Maritime Administration warned that Houthis continue to pose a threat to U.S. assets, including commercial vessels, in this region.

“Vessels with an Israeli, U.S., or UK association and any vessel within a group or company fleet structure where the company has been identified as making port calls in Israel could be at high risk of terrorism and other hostile actions from the Houthis when transiting the southern Red Sea, Bab el Mandeb Strait, and Gulf of Aden until further notice,” the U.S. Maritime Administration (MARAD) said in a maritime advisory.

Under the guidance, MARAD warns that potential hostile actions include one-way unmanned aerial vehicle attacks; unmanned surface vehicle attacks; unmanned underwater vehicle attacks; ballistic and cruise missile attacks; small arms fire from small boats; explosive boat attacks; and illegal boardings, detentions, and/or seizures.

U.S.-flagged commercial vessels operating in these areas are strongly advised to turn off their AIS transponders, unless vessel masters believe that doing so would compromise the safety of the vessel.

U.S. vessels operating in these areas are instructed to remain as far as possible from Yemen’s coastline without compromising navigational safety. Crewmembers should be especially vigilant when at anchor, operating in restricted maneuvering conditions, loitering, or proceeding at slow speeds.

Vessels emailed or hailed on VHF by the Houthis, or entities claiming to be Yemeni authorities, and instructed to divert from their course, activate their AIS, or submit voyage information, should ignore the email or call and continue their passage if safe to do so.

The vessel’s master should, if the safety of the ship and crew would not be compromised, decline permission to board, if the Houthis seek to board a U.S.-flagged commercial vessel in these areas, noting that the vessel is proceeding in accordance with international law, as reflected in the Law of the Sea Convention.

If vessels observe or hear a suspected UAV or missile or observe a small boat approaching with apparent hostile intent, crewmembers not needed for the safe navigation and operation of the vessel should be relocated to a safe space until the threat has passed. Additional precautions should be taken to ensure small boats are kept at a safe distance whenever possible.

U.S.-flagged commercial vessels operating in these waters are advised to conduct a pre-voyage risk assessment, incorporate appropriate protective measures into vessel security plans, exercise caution, and monitor the VHF Channel 16.

In the event of any attack, incident, or suspicious activity, vessels are instructed to activate the Ship Security Alert System and contact the U.S. Fifth Fleet Battle Watch and UKMTO.

The advisory will remain in effect from March 26 until September 22, 2026. The advisory supersedes and cancels U.S. Maritime Advisory 2025-012.