Boeing is to offer Qantas its larger 777X-9 for delivery in 2021 to launch its Project Sunrise non-stop flights from New York and London to Sydney as an interim solution suggest sources in the US.

The US manufacturer has slowed the development of its longer-ranged 777X-8 and will compensate Qantas for operating the larger 777X-9 with reduced payload to meet the range mission with just below 300 passengers.

The 777X-9 seats more than 400 passengers, depending on an airline's configuration choices and has a range of 14,185 km with that number aboard.

At a lower passenger number of 300, the range is extended to the 17,000km required for the ultra-long-range missions but additional, palatalized, fuel tanks may also be needed the sources suggest.

The smaller 777X-8, which will seat 350 passengers and has a range of 17,220 km.

Apparently the Boeing strategy of offering the larger 777X-9 will also enable Qantas to operate the flights a little earlier than the originally anticipated start date of late 2022 early 2023.

Recent cutbacks by Etihad Airways to its 777X order have freed up delivery positions.

While the 777X-9 is too big in the long term for the Project Sunrise mission the aircraft is now the largest aircraft available for an Airbus A380 replacement.

Boeing anticipates that Qantas would retain the 777X-9 as 777X-8s are delivered.

However, the Boeing offer faces very tough competition from Airbus with its A350-1000.

Qantas CEO Alan Joyce says the competition is very close.