You *must* have plib version 1.4.x or later installed on your system to build FlightGear!" Flight Gear is no longer compatible with the earlier versions of the library. You can get the latest version of plib from: http://plib.sourceforge.net Build notes: You should be able to just run "./configure" to configure the package and use all of plib's defaults. Then run "make" followed by "make install". By default, plib installs itself into /usr so if you don't like this, be sure to specify an alternate prefix such as --prefix=/usr/local