Typically it is the purchasing manufacturer that defines the FAI requirements for a manufacturer who is making a part for them. The burden of proving the part being purchased is built as required and that inspections and documentations are performed to the standard defined for the industry falls on the supplier.
Here is a sample notice from a customer to a supplier not meeting FAI requirements that you don’t want to receive:
Recent audit findings and defect investigations have identified deficiencies within (Your Customer’s Name) supply base related to First Article Inspections (FAI). (Your Customer’s Name) considers the First Article Inspection process both a fundamental and critical step in ensuring the manufacturing and subsequent inspection processes are capable of consistently producing a product that meets all engineering and contractual requirements.
This is not the type of notice you want to be receiving from your customer.