35 U.S.C. § 272 : US Code - Section 272: Temporary presence in the United States

Search 35 U.S.C. § 272 : US Code - Section 272: Temporary presence in the United States

The use of any invention in any vessel, aircraft or vehicle of
any country which affords similar privileges to vessels, aircraft
or vehicles of the United States, entering the United States
temporarily or accidentally, shall not constitute infringement of
any patent, if the invention is used exclusively for the needs of
the vessel, aircraft or vehicle and is not offered for sale or sold
in or used for the manufacture of anything to be sold in or
exported from the United States.