Shipping on Highest Alert After U.S. Strikes Iran. What Comes Next?

As of now, the Strait of Hormuz remains open to maritime traffic following U.S. strikes on Iran’s nuclear facilities on Sunday. However, commercial shipping in the region is operating under the highest threat levels in more than two decades.

In retaliation for the strikes, Iran’s parliament passed a motion to close the Strait — a vital trade artery through which roughly a fifth of the world’s oil and gas flows. The move still requires approval from the National Security Council, which has yet to be granted.

At least two tankers were tracked diverting from Hormuz transits on Sunday, while other shipowners sought to minimize time spent in the Gulf. 

On Sunday, the Joint Maritime Information Center (JMIC) raised the threat level for U.S.-linked commercial vessels in the Middle East from “elevated” to “high.”

Ships flagged, owned, operated, chartered, or carrying cargo connected to the U.S. were also advised to avoid the Red Sea and Gulf of Aden, further disrupting a second key trade chokepoint in the region.

Iran-allied Houthi rebels threatened on June 21 to resume attacks on U.S.- and Israeli-affiliated commercial maritime traffic if Washington escalated military action — effectively ending a ceasefire agreed in May.

Trade through the Red Sea and Suez Canal is already 60% below pre-Houthi attack levels from November 2023.

Strait of Hormuz: Sharp Drop in Activity

Windward data reveals that yesterday marked the lowest number of unique vessels entering the Strait of Hormuz since the beginning of the crisis — with a daily number of inbound voyages 28% lower than the weekly average. 

Outbound movements mirrored the trend, registering a 16% drop in daily departures compared to the past week’s average. These declines underscore heightened caution among shipowners amid geopolitical uncertainty and signal the growing impact of perceived risks on real-time maritime behavior.

GPS Jamming Is Broad-Based, Not Targeted (For Now)

An unprecedented spike in GPS jamming targeting ships’ Automatic Identification System (AIS) signals worsened over the weekend, with Windward data showing a sharp escalation in disruption across key maritime corridors.

Over a 24-hour period, more than 23% of commercial vessels operating in the Arabian Gulf and transiting the Strait of Hormuz experienced GPS jamming, disrupting navigation in international shipping lanes.

Windward’s analysis found that no vessel type, flag, or country of beneficial ownership was disproportionately affected — suggesting that as of now jamming is broad-based rather than targeted.

Key findings from the weekend include:

• A 60% surge in GPS jamming incidents, affecting 1,600 vessels—up from a daily average of around 1,000 between June 13–20.
  
• AIS signals were manipulated and redirected to locations along Iran’s coast, including Bandar Abbas, Bushehr, Asalouyeh, and offshore positions near Ras Al Khaimah, Shaam, and Bandar Siraf.

Among the affected vessels, 271 ships over 5,000 deadweight tons (dwt) experienced interference. The most impacted vessel classes by tonnage were crude oil tankers, followed by bulk carriers, product tankers, and LNG carriers.

Full breakdown of affected vessels as per Windward Maritime AI™ data:

Here’s a more detailed breakdown of the affected vessels:

• 47 crude oil tankers, including 31 VLCCs (each capable of carrying up to 2 million barrels of crude)
  
• 65 product tankers
  
• 57 bulk carriers
  
• 21 large containerships, including those on Asia–Middle East services
  
• 16 LNG and 18 LPG carriers

Ships beneficially owned by Greece — the world’s largest shipowning nation — were most affected, followed by those owned by Japan and China. The most impacted flags were the Marshall Islands, Panama, and Liberia, which are also the world’s top three open registries.

Of the 1,600 vessels affected by jamming, roughly 550 lacked IMO numbers, indicating that most were small craft, such as fishing vessels, tugs, pleasure boats, and minor coastal traders.

With threat levels rising and vessel activity declining, the coming days will be critical in determining whether these disruptions remain short-term precautions or the start of a more prolonged shift in regional trade dynamics.