As Boeing moves closer to issuing the go-ahead for the 787-10X, arguably one of the easiest marketing decisions it has faced in a decade, its customers and suppliers alike are still waiting for the other shoe to drop over the launch of the 777X.

Potential buyers of what will be the world's largest twin-engine airliner were briefed by the manufacturer at the start of November, around the same time as Boeing officially began talks about the 787-10X double-stretch derivative with airlines and leasing companies.

This time, Boeing quietly acknowledged it had received board approval to begin talks on the 787-10X without the normal fanfare traditionally associated with “authority to offer” (ATO). The move nonetheless is being widely seen as a clear signal of both Boeing's determination to stave off competition from the Airbus A350 as well as its growing confidence in the improving health of its 787 production system.

The stealthy aspect of the ATO remains equally intriguing, though it is believed to be more closely linked to a desire to firm up a batch of initial launch customers than any last-minute uncertainty over the final configuration. Boeing says clearance to start discussing the 787-10X is “conditioned upon our obtaining final board approval to launch the program at a yet-to-be-determined date.”

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.” Given the current schedule, unidentified potential customers say a firm launch decision is not expected from the Boeing board until early next year.

The 787-10X is a 787-9 stretched by 18 ft. to 224 ft. to seat an additional 43 passengers. Although jutting up against the Airbus A350-900 in capacity, the stretch is targeted as an A330 “killer” with exceptionally low seat-mile costs. The 320-seater is expected to be a 6,700-6,750-nm-range aircraft with a maximum takeoff weight slightly less than 7,000 lb. heavier than the 787-9 now in initial assembly.

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 trunk routes from the Middle East to Europe and Asia, as well as transatlantic services for carriers including British Airways and Singapore Airlines, which are among the early launch contenders. Assuming a firm launch decision in early 2013, entry into service is widely expected around 2018-19.

As the 787-10X forms part of Boeing's stated strategy to bracket the A350 between the double-stretch derivative and the 777X, the launch of one of the new aircraft will ultimately determine the go-ahead for the other. For Boeing, the key question on the 777X remains timing, and although the A350-1000 launch continues to show signs of sliding further into the second half of the decade, the main driver appears to be getting the technology decisions correct on its new, big twin derivative.

Compared to the relatively straightforward double-stretch of the 787-10X, the development of a pair of larger rewinged, reengined successors to its 777-200LR/300ER for possible entry into service in 2019 is a far greater gamble in terms of cost, technology and marketing tactics. As well as major choices concerning the use of composites in the wing and major system innovations, Boeing's arguably biggest single decision is whether to make the engine dual- or sole-source.

General Electric, in the pole position to supply the engines for the new derivative, is sticking to a technology test plan for the GE9X for the 777X, despite continuing uncertainty over Boeing's development timetable. The engine maker is running a raft of technology demonstration efforts to support FAR33 engine certification in 2018, and entry-into-service in 2019.

“Even though Boeing is still figuring out what they want to do, we're doing the technology,” says GE90 general manager William Millhaem. “It's the right thing to do for the industry.”

Although GE is also reluctant to give specific timetable details, it is expected to run the first version of a new core for the GE9X as early as 2014. A final “Toll Gate 6” decision on freezing the design will likely take place around 2015, with the first engine going to test in the 2016 timeframe. Given this timing, the engine would be tested on GE's Boeing 747-400 flying testbed in 2017 with certification the following year.

Key technology maturation tests in the run-up to the design of the new core include the planned evaluation of a 27:1 pressure-ratio high-pressure compressor (HPC). The initial version of an 11-stage unit will be tested at GE's oil and gas facility in Massa, Italy, in mid-2013, and will be the highest pressure-ratio compressor of its type yet developed for a GE commercial engine.

Testing of the advanced compressor rig will check the configuration “to look if anything unexpected happens at 27:1 and see what happens when we bleed air off and if we get the right clearances,” says Millhaem, who adds that the lessons will be used to improve the baseline design before the first core is built. The advanced “E3” (Energy Efficient Engine) 19:1 compressor developed with NASA was key to the success of the original GE90, while the evolved HPC of the GEnx has a pressure ratio of 23:1. Overall pressure ratio for the entire GE9X is similarly targeted at an ambitious 60:1, compared to 50:1 for the GEnx and 40:1 for the GE90.

“With the GE9X, we're continuing that strategy, but we are reaching into the technology cupboard to pull out new things from the 9X technology pool,” says Millhaem. “If we start with a scaled GEnx-1B, we get about halfway to what Boeing is asking us to do for the 777X,” he says. The 777X is targeting fuel burn around 10% lower than the current GE90-115B-powered 777, while maintaining existing maintenance costs.

Other work is focused on a fourth-generation fan that will operate at higher speed that the one in the current engine.