Cathay Pacific is boosting capacity between Hong Kong and Sydney from October 1 by replacing one of its existing A330 services with a larger B777-300ER.
The airline carried out the same upgrade on another of its four daily flights last year.
Slot restrictions in Australia prohibit the airline from adding extra flights onto the route, meaning an aircraft replacement is required in order to increase seat capacity.
The deployment of the B777-300ER will offer 90 more seats than the A330, including two more in business, 11 in premium economy and 77 in economy.
As reported by The Sydney Morning Herald, Cathay Pacific said there has been a growing demand for the airline's premium economy class on flights between Australia and European destinations.
Nelson Chin, the carrier's general manager, south-west Pacific, said: "Hong Kong is a stable market for us and we fly four times a day from here so we do get the biggest [market share from Australia].
"But the growth in the market we see is beyond Hong Kong. It is very much the connectivity to the other 22 destinations we fly to.
"We don't want someone getting on an A350 from Europe to Hong Kong and then coming down here on an A330 or a 777 and having a vastly different experience."