If after installing an aircraft you got an invisible aircraft, this problem usually happens in FSX when you don't have SP2 or Acceleration Pack installed.
You can get SP2 for free from this link: http://www.microsoft.com/Products/Games/FSInsider/downloads/Pages/default.aspx
(NOTE: If you also need Service Pack 1, which is an optional Service Pack but sometimes required by FSX, you can download it from this link: http://www.gamershell.com/download_19171.shtml )
If you are having issues with some missing panels, you could also try to re-install the aircraft running the installer as an administrator (and make sure you click "Run" and "Yes" when FSX prompts you to run the aircraft for the first time).
If you already have Acceleration Pack installed, try using the "Repair" option.
Finally, try installing the latest drivers of your graphics card.
Some users have been able to fix some invisible panel issues by following this guide:
We've detected that in some cases this issue is caused for a lack in RAM memory, try closing the simulator, closing another programs runing and then opening the simulator again, in extreme cases you'll need to add RAM memory to your machine.