For the developers of FlightGear who want to work on Linux (actually i think working on linux is better than working on windows using Visual Basic and trying to include every open source library), there are some things to do.
As mentioned on their website, source code of FlightGear has some dependencies, They are OpenSceneGraph, GLUT (FreeGlut), OpenAL, plib and SimGear. Every dependency is a distinct library but they are dependent to each other in some places. Anyway, if you follow the order in my sentence and install them one by one your Linux OS will be a suitable environment for developing FlightGear.
Usually the accepted method of "./configure", "make", and "make install" commands work fine. But you may need to have CMake installed as well because one of the dependencies needs CMake to be installed. By the way boost packet for C++ is also needed and you can find it googling. Anyway, it's easy to install CMake by typing command shell "sudo apt-get install cmake".
By the way i first tried to use Synaptic Package Manager of Ubuntu to install the dependencies. I found them but not the appropriate versions (i mean there were older versions) So, i tried to install them by the classic "./configure", "make", and "make install" methods. It's more complicated but safer when you do something yourself i think.
If you encounter a problem during any ./configure steps, it's potentially another dependency issue. I only encountered it once, trying to compile FlightGear manually. It said boost package for C++ is needed but it was easy to find it with a google search. Being an operating system spesific issue, maybe you may need to install some additional packages but the possibility is very low.
That is all needs to be done in order to have a suitable developing environment for FlightGear in linux. I don't think there is a need to mention that you have to have g++ installed on your machine also.
I haven't decided which IDE to use yet but I'm thinking on Eclipse to use, Eclipse seems fine.