What size registration marks can a small U.S. -registered aircraft built at least 30 years ago display?

The correct answer indicates that a small U.S.-registered aircraft built at least 30 years ago has the option to display either 2-inch or 12-inch registration marks. This flexibility is provided under FAA regulations, which state that certain aircraft manufactured more than 30 years ago are not required to adhere to the 12-inch registration marking size that applies to newer aircraft.

This allows owners of older aircraft to choose smaller marks (2-inch) for aesthetic reasons or to better suit the appearance of their aircraft, while still maintaining compliance with registration requirements. Smaller markings can be particularly appealing for vintage or classic aircraft designs, aligning with the preservation of the aircraft's original look.

In contrast, the limitations of the other choices stem from the fact that only the 2-inch and 12-inch sizes are permissible, as established by regulatory guidelines. Thus, the option that allows for both sizes acknowledges the unique status of these older aircraft under the FAA’s rules.