Key Highlights

  • Ship-to-ship transfers remain a key tool for moving sanctioned Iranian oil through global shipping lanes.
  • OFAC continues targeting vessels, traders, and intermediaries linked to Iran's oil export network.
  • Maritime analysts warn that aging shadow-fleet tankers increase environmental and insurance risks.

In some of the world's busiest maritime corridors, satellite imagery and vessel-tracking systems continue to reveal a persistent pattern: aging tankers meeting offshore to transfer oil between ships while attempting to obscure the cargo's origin. These operations form part of what analysts commonly call Iran's "dark fleet" or "ghost fleet," a network that has helped sustain Iranian crude exports despite years of U.S. sanctions.

How the Ghost Fleet Operates

According to guidance issued by the U.S. Treasury's Office of Foreign Assets Control (OFAC), ship-to-ship transfers are frequently used to disguise the origin of Iranian petroleum. Cargoes may be transferred multiple times between vessels before reaching their final destination, making enforcement and attribution more difficult.

Another common tactic involves manipulation of the Automatic Identification System (AIS), which normally broadcasts a vessel's location. Maritime investigators monitor unusual AIS gaps, identity changes, flag switches, and offshore rendezvous points as indicators of sanctions-evasion activity.

Recent investigations have identified transfer hubs in the Gulf of Oman, waters near Malaysia, and parts of the South China Sea, where tankers conduct offshore cargo exchanges before crude moves toward Asian buyers.

Why Enforcement Remains Difficult

The U.S. government continues to expand sanctions against vessels, trading companies, and facilitators connected to Iranian oil exports. In May 2026, Washington imposed fresh sanctions on multiple vessels and entities linked to Iranian petroleum shipments.

Yet enforcement challenges remain significant. Tankers frequently change ownership structures, flags, and operating companies. Some operate with unclear insurance arrangements, while others move through jurisdictions that have limited incentive or authority to enforce U.S. sanctions.

The result is a constantly evolving network in which sanctioned vessels can often be replaced faster than authorities can remove them from the market.

Growing Safety and Environmental Concerns

Beyond sanctions compliance, maritime experts increasingly focus on safety risks. Many vessels associated with shadow-fleet operations are older than the global tanker average and may operate with uncertain maintenance and insurance coverage.

Environmental groups and shipping specialists warn that a major spill involving an uninsured tanker could create substantial cleanup and Liability challenges. Offshore transfers conducted outside established safety zones add another layer of operational risk.

Conclusion

Iran's ghost fleet highlights both the strengths and limitations of modern sanctions enforcement. Commercial satellites, maritime analytics, and open-source intelligence have made ship-to-ship oil transfers far more visible than in the past. Yet visibility has not necessarily translated into complete deterrence. As long as discounted crude finds willing buyers and global shipping networks remain fragmented across jurisdictions, the dark fleet is likely to remain a significant feature of the energy market, maritime regulation, and geopolitical competition.