Cathay Pacific Airways, a major airline in Hong Kong, signed an agreement with Boeing on Tuesday to purchase six more 777-300ER aircraft with an estimated value of 12. 5 billion HK dollars (1.61 billion U.S. dollars) at list price.

The additional six newly purchased 777-300ERs will be delivered in 2013 and 2014.

With the new agreement, the airline has altogether ordered 36 of the aircraft type, including 18 already in service, primarily on long-haul and ultra-long-haul routes to Europe and North America, and another 12 scheduled for delivery from 2011 to early 2013.

"We are very pleased to confirm this purchase of six more Boeing 777-300ERs, a superb aircraft that has already significantly enhanced our operations on key long-haul routes," said Cathay Pacific Chief Executive Tony Tyler.

Cathay Pacific currently operates a fleet of 128 wide-body aircraft. Among them, aircraft by Boeing include 12 Boeing 777- 300s, five Boeing 777-200s, 22 Boeing 747-400 passenger aircraft and 25 Boeing 747-400 freighters, in addition to 777-300ERs.

Cathay Pacific announced earlier in the month it will also purchase 30 new Airbus A350-900 aircraft to enhance its mid-sized long-haul wide-bodied fleet. Delivery of those aircraft, valued at almost 61 billion HK dollars (7.86 billion U.S. dollars) at list price, will commence in 2016. This was the airline's biggest-ever single aircraft purchase.