Blender AC3D import and export
Many Flightgear aircraft modelers prefer Blender as their 3D editor. There is good support for import and export of flightgears native AC3D fileformat to and from Blender. This page gives an overview of those options.
Blender version 2.4
This Blender version support import and export of AC3D out of the box. Just go into user preferences and enable the addon scripts.
Blender version 2.5 to 2.62
For these version you can use these scripts by Majic79:
Blender version 2.63 and later
For version 2.63 till 2.74 you have more choices of scripts.
When exporting with this addon, notice that you should set UV and texture inside the material, not just inside the UV editor. See here on how to do that: Video showing how to apply UV texture for Majic79 addon
Inside Blender when you want to see the textures, be sure to set the shader to GLSL (or for 2.7 just set view mode to materials).
When exporting/importing, this addon will tessellate the meshes into quads/triangles.
Report bugs here, be sure to include problematic AC/blend files: Majic79 AC3D issues
Mr. No addon
When exporting with this addon, make sure you set the texture inside the UV editor.
When using this script, it is very important that everything is textured. The addon will silently fail if this is not the case.