AA is a Word property that indicates if the responding Domain Name Server is an authority for the Domain name space in the question section of a DNS query. 

AA is used in a DNS response that may contain multiple resource records in the answer section of the DNS response, and each resource record may have a different owner. AA corresponds to the name which matches the Omain name in the query, or the owner name for the first resource record in the answer section. 

AA is represented in a DNS header as a bit flag. Changing the value of AA ensures that the appropriate bit field is updated in the DNS header for the message packet.