Yes, there are 3D printed parts in the aerospace industry. One popular way to do this is FDM or Fused Deposition Modeling for composites. Nasa is currently testing rocket engine parts generated using 3D metallic printing.
Get obscure enough and you can find printed diamonds.
The OP's original post was about economical 3D metal printing. There are very few areas of Aerospace where using the adjective "economical" would be accurate. Being able to make 3D printed parts out of metal economically is still a very long way off. It took years before carbon fibre was able to move into mainstream and be considered economical. One of the first places carbon fibre appeared was Aerospace. Aerospace/defense pioneers many technologies.
I agree that currently it only makes sense to 3D print certain components. Many others are much faster and much more economically made by traditional manufacturing. However, that the printing of structural strength metal components can be done is a huge leap from the early years of weak, plastic models. It will only be a matter of time before it becomes economical to print almost everything. I believe that day is fast approaching. If you look at the growth curves of additive manufacturing, it is outpacing the growth of standard manufacturing several fold, and the trend is getting worse each year. I believe it will be much sooner than most want to believe. That's why I'm going long on several 3D printing companies. One of which is Dassault Systemes. That's your stock tip of the year.