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.

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.

Spirit AeroSystems said there is "substantial doubt about the company's ability to continue as a going concern" though Boeing and Airbus are planning to acquire portions of the parts maker.