The tankers quickly reflagged to the more obscure registries of Tanzania and the Pacific island nation of Tuvalu. They were also renamed: For instance, the Hirmand, flagged to Cyprus, became the Honesty, flagged to Tuvalu. They had new registered owners, too—an array of front companies in places ranging from the Seychelles to Tanzania to a post office box in Tuvalu.

In August 2012, Sens. Robert Menendez and Mark Kirk wrote a bipartisan letter to President Obama, urging him to blacklist the shipping registries of Tuvalu and Tanzania for “their participation in Iranian attempts to conceal the ownership and control of vessels owned or controlled by the National Iranian Tanker Company (NITC).” Tuvalu swiftly deregistered the Iranian tankers. Although Tanzanian authorities promised to do the same, the U.S. Embassy in Tanzania protested that the host government seemed to be registering many of the Iranian tankers deflagged by Tuvalu.

At the end of 2012, Tanzanian authorities denied that any blacklisted Iranian ships were still registered under their flag. But dozens of Iranian ships were using their onboard Maritime Mobile Service Identity systems to signal as Tanzanian—which is how most of the Iranian tankers currently sailing under no identified flag are signaling to this day.