Qantas Airways has ordered six Boeing 787 Dreamliners, worth more than $2 billion, to replace the last of its iconic but ageing fleet of 747 jumbo jets.

The airline said on Wednesday the order would bring its fleet of long-haul 787-9s to 14 aircraft by the end of calendar 2020, and see it withdraw from service the final six of its 747-400s not already slated for retirement. Investors cheered the news lifting Qantas shares by 8.1 per cent on Wednesday.

Qantas announced it would retire the five oldest of its 11 jumbo jets when it placed it first order of eight Dreamliners in 2015.

Chief executive Alan Joyce said the airline's strong financial performance in recent years had made it possible to order more Dreamliners, which are more fuel efficient than 747s and would give customers a better on-board experience while also opening up new network options.