Mich. Comp. Laws § 421.56

Sec. 56. "American vessel" as used in this act means a vessel documented or numbered under the laws of the United States, or a vessel which is neither documented nor numbered under the laws of the United States nor documented under the laws of any foreign country, if its crew is employed solely by 1 or more citizens or residents of the United States or corporations organized under the laws of the United States or of any state. "American aircraft" means an aircraft registered under the laws of the United States.