Boeing has begun formal talks with airlines and leasing companies on the development of the 787-10X double-stretch derivative following the provisional go-ahead from the company’s board of directors.

The move is “conditioned upon our obtaining final board approval to launch the program at a yet-to-be-determined date,” says Boeing. Responding to questions from Aviation Week, the company adds, “The timing of a decision to launch the program will depend on market response during the next phase of our discussions about the airplane.”

The 787-10X is stretched by 18 ft. over the 206-ft.-long 787-9 to seat 43 more passengers. Targeted as an Airbus A330 “killer” with exceptionally low seat-mile costs, the 320-seater is expected to be a 6,700- to 6,750-nm-range aircraft with a maximum takeoff weight of about 551,750 lb., just under 7,000 lb. more than the 787-9 stretch now in initial assembly.

The 787-10X is being offered with the 78,000-lb.-thrust-rated performance improvement package (PIP) II standard General Electric GEnx-1B engine or the Rolls-Royce (R-R) Trent 1000 TEN (thrust efficiency new technology) version. Certification work on the PIP II engine, which includes a higher-flow, low-pressure compressor, improved high-pressure compressor and durability upgrades to the high-pressure turbine, is nearing completion, with icing tests about to begin.

R-R, which earlier this year signed a memorandum of understanding with Boeing to offer the Trent 1000 TEN on the stretch, is targeting introduction of the 787-8/9 in the first half of 2016. The engine will incorporate newer design features from the R-R Trent XWB now in development for the Airbus A350, and saves a further 3% fuel burn over the company’s current Package B standard.

Boeing adds that it has been “working closely with airline and leasing customers to define the key capabilities and features of the 787-10X, and we anticipate strong market demand for this third and largest member of the 787 family.”

Primary markets are expected to be on trunk routes from the Middle East to Europe and Asia, as well as transatlantic service, with British Airways and Singapore Airlines among early launch contenders. Assuming a firm launch decision later this year, entry-into-service is widely expected around 2018-2019.

Sources add that “nobody is using the word offerability at this point,” though the Boeing sales teams are now “allowed” to speak to airlines and present detailed marketing data for a product now deemed ready to move from product development to firm launch. Approval to offer is thought to have been given at the most recent board meeting, believed to have been held late last month.