President Barack Obama has warned that Iran is not open for business, even as the United States has loosened some of its economic sanctions as part of an interim nuclear pact.
Yet, on Tuesday morning, a plane owned by the Bank of Utah, bearing a small American flag on its tail, was parked in a highly visible section of Mehrabad Airport in Tehran.
While federal aviation records show the plane is held in a trust by the Bank of Utah, Brett King, one of its executives in Salt Lake City, said, "We have no idea why that plane was at that airport."
He said the Bank of Utah acted as a trustee for investors who have a financial stake in the plane and that the bank was investigating further.
The Federal Aviation Administration said it had no information about the investors in the aircraft or who was operating it.
The Treasury Department's Office of Foreign Assets Control, the government's primary enforcer of sanctions against Iran, declined to comment on the plane's presence there. Under U.S. law, any American aircraft would usually need the department's approval to go to Iran without violating complicated rules governing trade.
Iranian officials also declined to comment on the purpose of the plane's visit or passengers' identities.
The secrecy surrounding the plane is compounded by federal aviation regulations that can make it virtually impossible to determine who was flying it.
The private plane, like thousands of others, is owned through a trust - a complex legal structure often established to help foreign individuals or corporations invest in planes that can fly freely within the United States.
King, who helps run the bank's trust services business, said the bank had no "operational control" or "financial exposure" to the plane. And he said he could not disclose the identity of the plane's investors.
King said Thursday that he was trying to get to the bottom of the aircraft's presence in Tehran.
"The Bank of Utah is very conservative, and located in the conservative state of Utah," he said. "If there is any hint of illegal activity, we are going to find out and see whether we need to resign" as trustee.