HONG KONG (AFP) - Hong Kong flag-carrier Cathay Pacific has ordered 21 long haul Boeing 777-9X planes at a list price of US$7.48 billion dollars (S$9.48 billion), the firm announced on Friday, as part of its fleet modernisation program.

The 777X series is Boeing's newest member of the 777 family, with advanced technology including new composite wings and new engines that consume 20 per cent less fuel than today's 777.

Cathay did not reveal the purchase price but airlines usually negotiate a discount from the catalogue price.

"The 777-9X promises us improved payload range capability and reduced operating costs, in addition to a significant reduction in environmental emissions," the airline's chief executive John Slosar said in a statement.

"Cathay Pacific is committed to modernising its fleet to provide a superior experience to passengers," Mr Slosar said, adding that the airline was "delighted to be an early customer" for the next generation of the 777 series.

The airline said the planes, which will be delivered between 2021 and 2024, will be ideal for long-haul destinations in North America and Europe.

"The huge investment we are making in new aircraft underscores... our commitment to maintaining Hong Kong's position as one of the world's great aviation hubs," Mr Slosar said.

The airline said in August it swung to a first-half lower than expected net profit of US$3.1 million, with passenger gains offset by persistently high fuel prices and falling cargo revenue.

The high price of jet fuel had affected its business adversely, it said in a statement then, adding that it had helped combat high fuel prices by withdrawing older planes and operating more long-haul services using fuel-efficient Boeing 777-300ER aircraft.

Starting from 2014, the airline is expecting the delivery of 12 Boeing 777-300ERs, and will see 50 of this aircraft type in its fleet by 2020.