Which of the following documents is NOT required for flight outside the US?

When flying outside the United States, pilots are required to carry certain documents to comply with both U.S. regulations and the regulations of the foreign countries to which they are traveling. Among these required documents are a medical certificate, a photo ID, and, if operating a radio, a radio operator's permit.

The pilot's logbook, while valuable for recording flight hours and experiences, is not required for legal flight operations outside the U.S. Therefore, it is not a mandatory document to carry for international flights. This makes it distinct from the other options, which are explicitly required for compliance with aviation regulations during international operations.