Published date: 8 March 2023


This Advisory Circular (AC) describes an acceptable means of compliance with Part 21 Subpart Q. Each reference to a number in this AC, such as 21.15, is a reference to a specific rule within Part 21. This material is intended for a product manufacturing organisation, or a person performing maintenance, in completing or replacing product identification markings.

Related rules

This AC relates specifically to Part 21 Subpart Q Identification of Products and Parts.

Change notice

Revision 3:

  • clarifies standards for data plates, serial numbers and other identification plates,
  • clarifies that Part 21 Subpart Q, Identification of Products and Parts, applies to Part 148 Manufacturing Organisations producing a type-certificated product,
  • corrects typos and other minor errors and clarifies requirements for Special Category aircraft,
  • formats this AC in line with current ACs, and
  • adds a Version History.