Europe’s Airbus has finalized an agreement to take some assets from Spirit AeroSystems, both companies said Monday, completing a critical part of a transatlantic carve-up of the struggling supplier with US rival Boeing.

European plane-maker Airbus will take over parts of Spirit AeroSystems as it and Boeing carve up the key supplier in an effort to improve production quality.

Airbus SE agreed to take over some assets and sites from Spirit AeroSystems Holdings Inc., clearing the way for the struggling US aerospace supplier to be acquired back by its former parent Boeing Co.