Airbus's A350 fuselage sub-assembly facility at St Nazaire has taken delivery of the first centre wing box for the new twin-jet type.
The wing box is manufactured at the airframer's site in Nantes and its construction included production of carbonfibre panels with an area of 36m2.
Carbonfibre components make up 40% of the box, which is 6.5m by 5.5m in planform, and 3.9m tall.
From Nantes the assembly is put on a transport jig and taken by barge - alongside an A380 centre wing box - along the Loire river to St Nazaire.
It will be fitted into the A350 fuselage and the sub-assembly flown by Airbus's A300-600ST transport to its new assembly line for the type at Toulouse.
A350 programme chief Didier Evrard said the delivery "marks a significant step forwards" for the aircraft. The 314-seat A350-900 will be the first member of the three-aircraft family to be assembled.
Spain's Airbus manufacturing plant at Puerto Real has also commenced production of a similar component for the first horizontal stabiliser.
The work involves construction of the lateral box - also primarily built from carbonfibre, with aluminium and titanium alloys - which measures 9.7m in length and up to 3.6m in width.
Lateral boxes, built in co-operation with Aernova, will be transferred to another Spanish facility, at Getafe, where they will be mated with elevators before being shipped to Toulouse.