The airline aims to maximize revenues on its ultra long-haul flights from Dubai to the U.S. west coast.

"We've been in dialogue with Boeing for almost four years about this, but recently we felt that the impetus from Boeing to improve the 777 extended range has slowed," Chief Executive of Emirates Airline Tim Clark was quoted as saying.

"We continue to remind them that we want an improvement to the extended range...or a new aeroplane," he added.

Clark said the airline do not consider the 747-8 Intercontinental any more, which is Boeing's new stretch version of the 747.

Emirates Airline had announced before that it needed a much larger aircraft to carry more passengers, like the 500-seat AirbusA380 or Boeing's new 747-8 Intercontinental, to replace the 266-seat Boeing 777-200 Extended Range version it now operates with direct services from Dubai to San Francisco and Los Angeles.

With a maximum range of more than 15,000 km, the 747-8 Intercontinental, or 747-8I, is capable of carrying up to 467 passengers. While cargo airlines have signed contracts for the freight variant of the 747-8, dubbed 747-8 Freighter or 747-8F, only German's Lufthansa has logged orders for the passenger version, The National said.

Earlier this year, Clark said he was only mildly interested in a proposal by Boeing to add a larger wing on the 777 and other modifications, saying he instead preferred a new design.

Emirates Airline, a major airline company in the Middle East, operates four of the world's longest nonstop commercial flights from Dubai to Los Angeles, Houston, San Francisco and the Brazilian city of Sao Paulo.