A350 being assembled at Toulouse, France
I'm going to start with the cranky part: it's NOT 3-D printing; it's 3-D fabrication, or technically FDM (fused deposition modeling).
Now that I've gotten past that part, here's the wonder: the technique is now being used to make strong, durable, less-expensive, lighter-weight parts faster...and they are made of a tough smoke- and flame-resistant resin.
The parts are being made by a subcontractor, Stratasys, and are going into the A350 XWB planes now coming off the Hamburg.
Photo: 3D fabricator Wikimedia / Zorro2212