Boeing insists its 777X programme remains on track for 2020 deliveries despite fresh engine issues that seemingly push the certification timeline toward the outer edge of the airframer's expectations.
During a press briefing on the first day of the Paris air show, Boeing executives repeatedly expressed contrition for two 737 Max crashes which killed 346 people and spurred the ongoing grounding of the aircraft.
"We are very sorry for the loss of lives as a result of the tragic accidents," said Boeing Commercial Airplanes chief executive Kevin McAllister. "Safety is sacred in this company."
He and other Boeing executives in attendance insisted that their prime goal was the "safe return" to service of the Max.
However, Boeing faces another challenge – keeping 777X development on track.
Immediately prior to the airframer's briefing, GE Aviation executives said a redesign of a stator in the GE9X's high-pressure compressor would likely push engine certification into the autumn. The GE9X powers the 777X.
"We found a component inside the compressor that had more wear than we anticipated," said GE Aviation chief executive David Joyce. "We pushed the pause button with Boeing."
After redesigning the stator, GE Aviation will resume engine tests.
"We are pretty confident we can get through the testing this year," says GE Aviation vice-president and general manager of commercial engines operation Bill Fitzgerald. "It will be later in the fall, I think."
That seemed the represent a notable delay to the timeline of the 777X, an aircraft which observers had expected would already be flying.
Assuming that GE Aviation certificates the GE9X in fall, and that the 777X's certification takes a year (as well-executed certification programmes tend to), regulators would sign off on the 777X in autumn 2020.
The Max crashes have intensified the pressure on regulators to ensure the safety of all new aircraft.
Nonetheless, Boeing is sticking to its previously stated 777X timeline.
"We still expect to have the airplane flight test this year, with an entry into service next year," says McAllister.
"It's too premature at this point to make any expectations relative to timing of this programme." he adds, citing the need to learn more from GE Aviation.
"We are staying very close to the situation with GE as they learn, relative to this, what the findings are."
As if Boeing does not face enough pressure, Airbus has announced the launch of the A321XLR – a response to Boeing's New Mid-market Airplane (NMA) proposal.
Airbus chief commercial officer Christian Scherer said at the show that developing the A321XLR would cost a "small fraction" of designing a clean-sheet aircraft like the NMA.
Boeing has not officially launched the NMA, though executives say studies continue. But they also say the proposed programme remains secondary to the Max's return to service.
Indeed, Air Lease executive chairman Steven Udvar-Hazy has described the NMA as being in "cold storage" amid the Max crisis.
Boeing's McAllister indicates that work on the NMA is active.
"We continue to work on the business case for the NMA," he says, adding that the proposed aircraft would have "twin-aisle comfort with single-aisle economics".
The design, reported to include 4,000-5,000nm range (7,400-9,300km) and capacity for 200-270 passengers, would make the aircraft best-suited to filling the middle-of-market hole, McAllister says.
Boeing has said it intends to decide whether to offer the NMA this year, and to formally decide whether to launch the aircraft in 2020.
But first Boeing must get the Max airborne. And executives concede they must regain industry and passenger trust.
"We are committed to learning from this," says chief commercial officer Greg Smith. "The safe return of the 737 Max to service has been priority one."
The company has enlisted "outside experts" to assist with technical and strategic issues related to its Max efforts, with an intent to "restore the confidence of our stakeholders".
Boeing has developed an update to the Max flight control software which it says will prevent similar accidents in the future. It also developed "advanced training materials" for pilots, McAllister notes.
"We have taken the time to do this right," he says.