The FAA has really defined in sometimes confusing definitions of what it means for a company to be a US citizen. Many companies may not need that test, but wish to register a FAA in number aircraft. In order to do so, the most common tool used is an owner trust, wherein the aircraft trust is actually a US citizen, and the beneficiary of the trust is the company that seeks the in registered aircraft operation, but is not a US citizen. This is a tool that has come under some scrutiny by the FAA in recent years, although they have confirmed the availability of the trust structure. It does newly require the trust to retain significant knowledge about the location of the aircraft, and the aircraft flight logs and maintenance logs in order to assure that they’re not running afoul of any Department of Defense or Department of Homeland Security regulations.