"Within Cathay Pacific, the Second Officer is considered an integral part of the flight crew with specific responsibilities. The primary functions of the Second Officer are to act as a cruise relief pilot, to monitor all facets of the operation and to support the crew. Second Officers operate on Cathay Pacific's fleet of Boeing 747-400 and Airbus A340-300 and A340-600 aircraft, operating worldwide on longhaul routes. "
This is what seen in CX's website