Which letter size must aircraft registration and markings typically be on fixed wing aircraft?

For fixed wing aircraft, the aircraft registration marking must be in a size that is clearly visible and readable. The regulations specify that the registration marks must be at least 12 inches in height when applied to the exterior of the aircraft. This size ensures that the numbers and letters can be identified easily during inspections and for identification purposes while the aircraft is in operation. The visibility of aircraft markings plays a crucial role in safety and compliance with aviation regulations, making it essential for them to be as prominent as possible. Smaller sizes, such as 2-inch, 3-inch, or 6-inch, do not meet the regulatory requirements for visibility and legibility, which is why they are not acceptable.