3-D printing is already being used for some airplane parts. A Wall Street Journal article, Next 3-D Frontier: Printed Plane Parts, provides details (behind paywall).
Here are some details on the types of parts currently printed:
[The] Pratt & Whitney aircraft-engine unit is using the process to make blades and vanes in compressors inside jet engines. Honeywell’s aerospace unit employs it to build heat exchangers and metal brackets but expects to find far more applications…
Boeing already makes about 300 different smaller aircraft parts using 3-D printing, including ducts that carry cool air to electronic equipment. Some of these ducts have complicated shapes and formerly had to be assembled from numerous pieces, boosting labor costs.
The biggest challenge is that 3-D printing is slow for long runs and expensive for some types of metals and plastics. What is needed for wider use?
But so far, despite lots of recent hype, 3-D printing is an infinitesimal sliver of global manufacturing, and experts say it will have to get much faster and cheaper before it can account for a sizable chunk of industrial production.
So, the technology has to get cheaper and faster.
Not a problem.
One thing you can count on technology to do is always get cheaper and faster.
Check out the full article.