N-numbers, the registration numbers for U.S. aircraft, adhere to specific guidelines:
- Format: Consists of the letter “N” followed by one to five alphanumeric characters.
- Numeric Start: The initial character must be a number (excluding zero).
- Character Limit: The total number of characters (excluding the “N”) cannot exceed five.
- Letter Placement: Letters can be placed at the end of the number, with a maximum of two letters.
- Reserved Numbers: N1 to N99 are reserved for FAA use.
- Obsolete Prefixes: NC, NX, NR, and NL are no longer issued.
Additional Considerations:
- Legibility: The N-number must be clearly visible and readable from a distance of 500 feet during daylight.
- Placement: Typically displayed on the tail of the aircraft but can also be on the fuselage.
- Color Contrast: The N-number should contrast with the aircraft’s color for visibility.
For detailed information and visual examples, refer to the FAA’s guidelines: