On which type of aircraft should the registration marks be displayed on the fuselage below the window line?

The registration marks for aircraft must be displayed prominently to comply with regulations, and the specific location can vary based on the type of aircraft. In the case of helicopters and gyroplanes, the registration marks are required to be placed on the fuselage below the window line. This positioning helps ensure visibility while maintaining the aesthetic and operational aspects of the aircraft.

On the other hand, airplanes typically display registration marks in different locations, which can vary based on design regulations. Hang gliders, with their lightweight and portable design, may have different requirements concerning mark placement. Balloon aircraft, due to their unique structure and operation, also have distinct guidelines for marking registration that differ from those of helicopters and gyroplanes. Therefore, identifying the appropriate placement for each type of aircraft is essential for adherence to aviation regulations.