Qantas has chosen Airbus' A350-1000 as the aircraft it will use for non-stop flights from Australia's east coast to New York and London, but delayed a decision on whether to go ahead with the new routes by three months.

The airline on Friday said the Airbus jet had beaten Boeing's 777X-8 as the preferred aircraft for its so-called "Project Sunrise" flights, which will be the longest commercial airline routes in aviation history.

Qantas has not yet placed a binding order, but says it will buy up to 12 of the Airbus jets if it goes ahead with the ultra-long haul flights.

Airbus will install an extra fuel tank in the A350-1000 and increase its maximum takeoff weight to be able to operate Qantas' missions.