Spec 2000:

Spec 2000 is a set of specifications, products and services designed to streamline the commercial airline industry's global supply chain. Widely used by airlines, manufacturers, suppliers and repair organisations, Spec 2000 is administered by the Air Transport Association (ATA) on behalf of 12 international industry associations and is the industry standard for procurement, repair and maintenance transactions. Guidelines on tracking are contained in Chapter 9, “Automated Identification and Data Capture” (AIDC), which includes standards on marking and identifying products with linear and two dimensional (2D) codes to provide automated means of storing and retrieving unique historical information.

Although linear codes 39 and 128 are the preferred codes for permanent part marking, the standard recommends that, in cases where the marking area is limited, 2D Data Matrix codes may be used.

Chapter 9 of Spec 2000 states,

"The bar code should remain on the part through the entire life of the part. It should also be readable with a commercially available standard contact or non-contact reader or scanner."