Airbus's increasing concerns over maturity of A350 components has finally translated into an inevitable programme delay, with entry into service of the -900 variant pushed back by up to six months.
Final assembly of the -900, which Airbus had been trying to begin by the end of 2011, will instead start in the first quarter of 2012.
The airframer, which had admitted previously that it had burned up its A350 schedule margins, has also shifted entry into service with Qatar Airways from end-2013 to the first half of 2014.
A350 programme chief Didier Evrard stressed that the "top priority" was to "reach the highest levels of part-readiness" before final assembly starts on the first airframe. The static aircraft will undergo final assembly first, followed by MSN001, the initial flight prototype.
Structural section maturity charts, displayed during an A350 technical presentation in Toulouse, indicated that bottlenecks included the trailing edge and centre fuselage.
Evrard admitted that some suppliers were having "more problems than others" with maintaining the original pre-final assembly schedule, set for August-September, when Airbus planned to gather all the primary components.
While Evrard declined to single out specific manufacturers, he pointed out that the centre fuselage section - the large composite panels for which are manufactured by Spirit AeroSystems - is the "most complex section", because it handles much of the wing-fuselage stress loading. Airbus is expecting to receive the initial panels from Spirit this month.
GKN supplies the trailing edge and recently delivered its first set of spars to the A350 wing plant at Broughton in the UK.
Evrard said that Airbus had spent the last three months managing a "kind of trade-off" whereby it closely examined which items it could accept without an impact on lead time.
"We cannot allow too much outstanding work to travel to the final assembly line," he added.
The airframer stressed that it wants a "manageable amount" of out-of-sequence work and that its maturity strategy has included joint improvement plans to focus on detailed parts and second-tier suppliers, and ensuring quality of assembly and installation drawings.
Evrard said Airbus did not want to "compromise" on the quality of drawings "despite the pressure of time".
"We're reaching the end of a critical step where we have to gather [main components]," he said, adding that the airframer is "satisfied" with the situation, "even if not everything is nominally on schedule". But he said the A350's development was "still a long journey" from completion.
Thirty-nine airlines and lessors participated in a programme progress review at the end of September, and Evrard said this allowed participants to "see a difference" in the A350's progress, with systems testing already under way on the "iron bird" as part of the effort to optimise maturity.
Six A350 customer airlines - Emirates, Finnair, TAP Portugal, United Airlines, US Airways and Qatar Airways - have also been participating in an "airline office" since April aimed at validating operations with the type ahead of service entry.
The work includes assessing and developing ground-support equipment, maintenance manuals and minimum equipment lists, highlighting potential operational impacts and finding ways to mitigate them.
First flight of the twinjet has moved to the first half of 2013. The airframer has not changed the nominal timing regarding the length of the flight-testing but said it would "refine" the details between final assembly and the maiden flight.