The thing with the airport building is not a bug. X-Plane relies on the user community and software developers to create scenery for airports. In turn, we get much more accurate airport mockups than we otherwise would have it autogen was used. There a plenty of airports available at x-plane.org (you'd have to sign up), and thousands of airports included in the default X-Plane installation from previous updates. When I first started out with X-Plane, this was a surprise to me, as well, but I found pretty much all of the airports I needed and even made one myself :).
As for the 747 spinning, I was sure that bug was fixed, but perhaps not. Report that issue as soon as it happens again here: http://dev.x-plane.com/support/bugreport.html
Make sure to include the log.txt file in the root X-Plane 11 folder! This will help the developers to fix the issue if it is reported by other users, as well.
As for the FPS drops, this could be caused by a variety of issues. Make sure your computer is not trying to execute other programs that are taking up performance other than X-Plane; while we're on it, how much VRAM does your GTX960 have?