Aircraft trusts are used for many reasons, but a common one is to meet legal aircraft registration requirements. US law restricts ownership of US registered aircraft by non-citizens. For companies, US citizenship relates to who owns or controls the company. One type of trust registration, known as a voting trust, involves a company which desires to own an aircraft, but is not a US citizen in effect becoming a US citizen by transferring enough control over the company to a US citizen trustee. Another option, called an owner trust, involves having a US citizen trustee themselves hold title to the aircraft. Both of these mechanisms have been sanctioned by the FAA, but involve detailed technical requirements and should not be attempted without professional guidance.