What may an export certificate of airworthiness be issued for?

An export certificate of airworthiness serves specific purposes under aviation regulations. It is primarily a declaration from the national aviation authority that an aircraft, engine, propeller, or component meets the airworthiness requirements for export.

When it comes to option C, it highlights a unique scenario where an engine or propeller may be deemed not airworthy according to standard criteria, but could still be exported if the country receiving it has different standards and accepts the non-airworthy status. This reflects the flexibility in international aviation practices, where different countries may have varying regulations regarding airworthiness.

The issuance of such a certificate allows for the trade of aviation parts that may not meet the exporting country's standards but can still be utilized in another jurisdiction. Understanding this is crucial for those involved in the international sale of aircraft and components, ensuring compliance with both local and foreign regulations.

The other options are narrowed down in their applicability. A pertains to the broader requirements for exporting aircraft but does not acknowledge the special considerations that may arise with non-airworthy components. B limits the context strictly to airworthy items, which does not capture the full scope of possible transactions. D is overly generalized, as not all aircraft can be exported unconditionally without regard to airworthiness requirements.