A U.S. applicant may present foreign-registered U.S. State of Design aircraft for demonstration of compliance to FAA regulations. However the applicant must present documentation showing the State of Registry's consent, or FAA must request permission from the State of Registry, to install the STC on the aircraft. A foreign registered aircraft may not be presented for inspection or test unless the State of Registry has agreed to and identified its requirements for acceptance of the modification, in accordance with ICAO Annex 6, paragraph 8.6. Some countries with whom the FAA has a bilateral agreement require their validation of the FAA STC.
If the proposed STC involves manufacturing outside the United States, the FAA must also determine whether accepting this project would impose an undue burden on the FAA. An Undue Burden decision is the tool FAA uses to make this determination. It is drafted by the FAA based on information provided by the applicant.