Mass Tanker Communications Blackout Reported in Persian Gulf Amid US-Iran Nuclear Talks

On the evening of May 24, 2026, Automatic Identification System transmissions near the UAE port of Fujairah — one of the world's largest bunkering and oil storage hubs — collapsed. Maritime tracking firm Windward AI reported that AIS signals from tankers and commercial vessels in the area had gone silent en masse, creating a visibility blackout across a critical stretch of the Persian Gulf [1]. Hours later, President Donald Trump announced that Washington and Tehran had "largely finalized" a memorandum of understanding for a bilateral peace agreement [2].

The two events are connected by more than timing. They sit at the intersection of a months-long maritime crisis in the Strait of Hormuz, an Iranian bid to assert sovereign control over the world's most important oil chokepoint, and nuclear negotiations whose outcome will shape global energy security for years to come.

The Blackout: Scale, Duration, and Mechanisms

AIS — the Automatic Identification System — is the backbone of global maritime surveillance. Every commercial vessel over 300 gross tonnes is required under international maritime law to broadcast its identity, position, speed, and heading. When those signals disappear, vessels become invisible to tracking platforms, port authorities, and other ships.

Windward AI's data paints a picture of escalating signal degradation across the Gulf throughout May 2026. On May 2, the firm recorded 671 AIS-dark incidents in a single day, with a seven-day rolling average of approximately 470 daily [3]. By May 5, satellite imagery revealed 167 commercial-size vessels near the Strait of Hormuz, of which 146 — roughly 87% — were operating dark and largely stationary [3]. Near Fujairah specifically, approximately 470 vessels were affected by GPS jamming within a 24-hour window, with three newly identified interference zones detected [3].

The May 24 blackout that preceded the Trump announcement was a continuation of this pattern but with heightened intensity. Windward described it as a convergence of "heightened electronic warfare, jamming, deliberate AIS shutdowns and intense cyber interference" [1].

Jamming vs. Spoofing vs. Voluntary Shutdown

Maritime intelligence analysts distinguish between three types of AIS disruption [4]:

• AIS deactivation ("going dark"): The transponder is switched off entirely. The vessel disappears from tracking systems but does not actively deceive them.
• AIS spoofing: The transponder remains active but broadcasts falsified data — fake positions, altered vessel identities, or fabricated flag state information.
• GPS jamming: External electronic interference degrades or blocks GPS signals, causing AIS position data to become unreliable even when transponders are active.

All three have been documented in the Gulf. Windward's April 6 intelligence report identified 267 AIS-dark events in a single day, alongside 44 injected signal zones and 92 denial areas [5]. Roughly one in ten vessels operating in the Gulf showed "anomalous" AIS behavior [5].

Historical Comparison

The current blackout dwarfs previous incidents. During the June 2019 tanker attacks in the Gulf of Oman — when the Front Altair and Kokuka Courageous were struck — AIS disruptions were localized and temporary, affecting dozens of vessels rather than hundreds [6]. The 2022 spike in dark vessel activity tied to Russian sanctions evasion involved systematic transponder shutdowns by individual tankers in the "shadow fleet," but occurred over months rather than in concentrated bursts [7]. The 2026 pattern is qualitatively different: a regional-scale, multi-mechanism disruption affecting hundreds of vessels simultaneously.

The 1.35-Million-Barrel Transfer

Amid the blackout, one transaction stood out. On May 24, a single VLCC — a Very Large Crude Carrier capable of holding approximately 2 million barrels — departed Fujairah carrying 1.35 million barrels of crude destined for South Korea [1]. At current Brent crude prices of approximately $104–$112 per barrel, that cargo is worth between $140 million and $151 million [8][9].

Windward called it "the first signal of flow resuming out of Fujairah since the announcement" of the Iran deal framework [1]. The specific vessel and the identity of the buyer and seller have not been publicly disclosed, consistent with the opacity that has defined Gulf trading during the crisis.

Source: Windward AI

Data as of May 5, 2026CSV

The transfer's significance is measured against the collapse in Fujairah exports over the preceding weeks. Normal daily exports from the port average 3.5 to 4 million barrels. On May 4 — the day of a reported attack on port infrastructure — departures fell to 1.22 million barrels. By May 5, they had cratered to approximately 500,000 barrels [3]. The May 24 VLCC loading, while far below baseline, represented a tentative resumption.

Who Is Most Exposed

The Strait of Hormuz carries approximately 20 million barrels of oil per day — roughly one-fifth of global petroleum liquids consumption — along with about 20% of the world's liquefied natural gas trade, primarily from Qatar [10].

The dependence is not distributed evenly. Japan sources 95% of its crude oil imports from the Middle East, with 1.6 million barrels per day flowing through Hormuz [10]. South Korea channels approximately 68% of its crude imports — some 1.7 million barrels daily — through the strait [10]. India, the world's third-largest oil consumer, imports about 50% of its crude through Hormuz, amounting to 2.6 million barrels per day [10]. China, as the world's largest crude importer, sources roughly half of its 11-million-barrel-per-day import volume from Middle Eastern suppliers and purchases over 90% of Iran's oil exports [10].

Source: EIA / Atlas Institute

Data as of May 25, 2026CSV

Collectively, China, India, Japan, and South Korea account for 69% of all crude oil and condensate flows through the strait [11]. Europe's direct crude exposure is lower, but Qatar sends nearly all of its LNG exports through Hormuz, creating a separate vulnerability for European gas markets [10].

South Korea maintains strategic petroleum reserves equivalent to 200 days of supply [10]. Japan and other IEA members hold similar reserves. But reserves are designed for short-term disruptions, not for the kind of sustained constriction the Gulf has experienced since early 2026.

Iran's Strait Authority and the Legal Dispute

The immediate trigger for the May blackout was the launch, on May 20, of Iran's Persian Gulf Strait Authority (PGSA) [12]. Overseen by the Islamic Revolutionary Guard Corps Navy, the PGSA functions as a self-declared sovereign regulator of Hormuz transit. Vessels must submit ownership details, insurance documentation, crew manifests, cargo declarations, and intended routing to the authority. A transit permit is issued only after approval — and after a fee is paid [13].

No official tariff has been published, but reports indicate some vessels have already paid up to $2 million per transit, with payments made in Chinese yuan [14]. The US Office of Foreign Assets Control issued an advisory on May 1 warning that such payments expose both US and non-US persons to sanctions risk [13].

The legal basis for the PGSA is contested. Under the UN Convention on the Law of the Sea (UNCLOS), ships of all nations have the right of "transit passage" through international straits — a standard deliberately stronger than "innocent passage" that prohibits coastal states from charging fees or conditioning access [15]. However, Iran signed UNCLOS in 1982 but has never ratified it. Tehran's position is that the transit passage regime is a "package deal" applicable only among UNCLOS parties, and that Iran retains the right to impose the more restrictive innocent passage standard, which can be suspended [15][16].

International legal scholars have largely rejected this argument. Chatham House and the European Journal of International Law have published analyses arguing that transit passage rights through Hormuz have achieved customary international law status, binding Iran regardless of ratification [16][17]. The United States, Gulf Cooperation Council states, and the European Union have all formally rejected the PGSA's legality [13].

The Insurance Crisis

The financial architecture of Gulf shipping has been reshaped by the crisis. Before February 28, 2026, the standard war risk premium for a vessel transiting the Strait of Hormuz ranged from 0.02% to 0.125% of hull value [18]. By mid-March, that figure had surged to 2.5% — an increase of more than 2,000% [18]. For a $120 million tanker, the per-voyage premium rose from as little as $24,000 to between $600,000 and $1.2 million. VLCCs carrying Saudi crude to Asia face transit bills of $7.5 million to $14 million [18].

On March 3, the Lloyd's of London Joint War Committee added the entire Persian Gulf, Gulf of Oman, and adjacent waters to its Listed Areas designation [18]. Within 72 hours, all twelve members of the International Group of Protection and Indemnity Clubs cancelled war-risk coverage for vessels in the region [18]. This effectively made commercial Gulf transit uninsurable through standard markets.

The World Economic Forum reported that governments have been forced to step in as "insurers of last resort," with state-backed guarantees emerging as the only mechanism to keep some trade flowing [19]. The Lloyd's Market Association has stated that safety concerns — not insurance availability per se — are the primary driver of reduced vessel traffic, though the distinction is academic when both factors point in the same direction [20].

Source: FRED / EIA

Data as of May 18, 2026CSV

WTI crude has risen 75.4% year-over-year, trading at $112.25 as of mid-May 2026 [9]. Brent crude has fluctuated between $95 and $114 per barrel in recent weeks, with sharp drops coinciding with optimistic signals from the US-Iran talks [8].

The Nuclear Talks: Where Things Stand

The US-Iran negotiations that form the political backdrop to the Gulf crisis have followed a tortured path. Direct talks began in 2025 and intensified through early 2026, with multiple rounds held in Oman and Islamabad [21]. On April 7, 2026, the two sides announced a temporary two-week ceasefire following military conflict earlier in the year. Trump subsequently extended the truce without setting a deadline [21].

The core sticking point is uranium enrichment. Iran holds approximately 400 kilograms of uranium enriched to 60% — below the 90% weapons-grade threshold but far above the 3.67% limit set by the 2015 Joint Comprehensive Plan of Action [22]. Washington's position has been "zero enrichment" — a maximalist demand that Iran has flatly rejected [22]. Tehran has indicated that while the level of enrichment is open for discussion, its fundamental right to enrich is non-negotiable [22].

The Arms Control Association published an analysis in April 2026 arguing that US negotiators were "ill-prepared for serious nuclear negotiations," having entered talks without a clearly defined fallback position between zero enrichment and the JCPOA's terms [23]. In May, Iran threatened to enrich to 90% if the US resumes military strikes, a statement that came after Trump rejected Iran's latest peace proposal as "completely unacceptable" [22].

Trump's May 24 announcement of a "largely finalized" memorandum of understanding appears to represent a shift, though details of the terms remain undisclosed.

Is This Routine? The Steelman Case

A significant counterargument exists: AIS shutdowns in the Persian Gulf are not inherently unusual. Tankers routinely disable transponders to obscure cargo origin for sanctions compliance or commercial confidentiality. Iran-linked vessels in particular have long employed "going dark" as standard practice. Kpler, a commodity data analytics firm, documented in November 2025 that AIS spoofing had become "a core tactic in global sanctions evasion," with 80.1% of ships caught spoofing subsequently sanctioned within a year [7].

The dark period for Gulf-to-Southeast-Asia transits typically spans 10 to 13 days from departure at Persian Gulf loading terminals [5]. Iran-domestic short-sea vessels — cargo ships, landing craft, service vessels — accounted for the majority of dark vessels identified in May 5 satellite imagery, and these vessels routinely operate without AIS [3].

The question is whether the May 2026 frequency exceeds the established baseline. The evidence suggests it does, substantially. A peak of 671 dark incidents in a single day, combined with multi-mechanism electronic warfare including GPS jamming affecting 470 vessels simultaneously, goes well beyond the pattern of individual sanctions-evasion shutdowns [3]. Windward's assessment that maritime visibility has "collapsed" rather than merely degraded reflects a qualitative shift [3].

Contingency Options: Pipelines, Escorts, and Alternatives

If the Strait of Hormuz becomes permanently constricted, the alternatives are limited.

Saudi Arabia's East-West pipeline (Petroline) connects the eastern Gulf coast at Abqaiq to the Red Sea port of Yanbu across roughly 750 miles. As of March 2026, it was operating at its full design capacity of 7 million barrels per day, with about 5 million barrels per day of crude exports via Yanbu and 700,000 to 900,000 barrels per day of refined products [24][25]. The UAE's Abu Dhabi Crude Oil Pipeline (ADCOP) provides additional bypass capacity.

Combined, these pipelines can move only a fraction of the approximately 20 million barrels per day that normally transit through Hormuz [10][24]. The Atlas Institute estimates that prolonged closure would push two-thirds of current Gulf crude exports into extended rerouting around the Cape of Good Hope, adding weeks and substantial cost to every voyage [10].

Naval escorts represent another option. The US Fifth Fleet, based in Bahrain, has maintained a continuous presence in the Gulf. During the 1987–88 "Tanker War," the US Navy conducted Operation Earnest Will, escorting reflagged Kuwaiti tankers through the strait [6]. A similar operation today would face a more capable Iranian military, including anti-ship missile batteries, fast attack craft, and mine-laying capabilities.

The current US approach has prioritized diplomatic resolution over military escalation, consistent with the broader trajectory of the Trump-era talks. Whether that posture holds depends on whether the "largely finalized" memorandum of understanding translates into a durable agreement — or collapses into another round of threats and counter-threats over the waterway that carries one-fifth of the world's oil.