A Request From Moscow

Appleby, based in Bermuda, is one of the world’s largest offshore law firms. Its files offer a rare inside look at more than a dozen aircraft trusts structured by American financial institutions for privacy-seeking plane owners, primarily foreigners who otherwise would not be allowed to register with the F.A.A. There is a premium on American registration because it increases a plane’s resale value, the bureaucratic requirements are less costly and complex, and it is believed to draw less scrutiny as the aircraft moves around the world.

Among the plane owners seeking Appleby’s services were Shaher Abdulhak, a Yemeni businessman worth an estimated $9 billion whose investments included a Coca-Cola distributor in the Middle East; UPL, an Indian producer of industrial chemicals and pesticides; and Rashid Sardarov, a Russian oil billionaire and longtime client of Mossack Fonseca, the law firm whose leaked records in 2015 became known as the Panama Papers.

In serving these clients, files show, Appleby dealt with the two banks that are the most prolific creators of American aircraft trusts: Wells Fargo and Bank of Utah. It is easy to see how Wells Fargo, the third-largest bank in the United States, with nearly $2 trillion in assets and offices in 42 countries, might find a lucrative niche catering to the wealthy elite. Less obvious is how Bank of Utah, with 18 branches confined to one state, took the same path.

As it happens, a group of former Wells Fargo trust officers joined Bank of Utah about 10 years ago and created what would become a profitable part of the bank’s business. The bank collected $8.8 million in trust fees in 2016 — an increase of $1.1 million from the previous year, according to its most recent annual report.

Mr. Croasmun and Mr. Hansen took issue with the suggestion that they were exploiting a loophole to bypass restrictions on foreigners registering aircraft in the United States. By filling the role of “U.S. citizen” for registration purposes, the bank provided a valuable service for, say, multinational companies whose top executives might not be American, they said. The bank is clearly sensitive to concerns raised about the trusts. Its website carries a statement distancing itself from the planes it registers in its name, noting its only role is that of trustee.