 This definition covers all activities for which aviation regulations require  issuance of a maintenance release document (aircraft certificate of return to service – CRS).
<fluency>  This definition covers all activities for which aviation regulations require  issuance of a maintenance release document (aircraft certificate of return to service – CRS).
 This definition covers all activities for which aviation regulations require the issuance of a maintenance release document (aircraft certificate of return to service – CRS).