What was found
(CAN) AFTER RETURNING FROM A FLIGHT, THE OPERATOR NOTICED A PIECE APROX 4-6 INCHES WIDE OF THE SHROUD SKIN PN C6W1007-37 WAS MISSING, JUST OTBD OF STN 135. THIS SHROUD SKIN IS SECONDARY STRUCTURE. OPERATOR WAS INSTRUCTED TO DO A VISUAL INSP FOR CRACKING OF THE UPPER AND LOWER SHROUD SKINS ON BOTH WINGS. OPERATOR WAS INSTRUCTED TO EITHER REPLACE THE DAMAGED SKIN WITH A NEW SKIN OR COULD OFFER A REPAIR DESIGN TO SPLICE IN A SKIN SECTION. OPERATOR ASKED FOR MORE DETAILS OF THE POTENTIAL CAUSE OF THE FAILURE AND THE OPERATING ENVIROMENT OF THE ACFT.