added *not* to use google earth like mentioned by alfonsodg
Once Flightgear has been started, fly with the UFO to the place you want the model to be positioned.
You must be sure about the size of the object in reference with the scene, it means: try to obtain the right value using some tools. Particulary, i recommend combine Googleearth and the rule tool and some size definition in the 3D software for obtain the right size, in my case, i have use Blender and the Caliper script. -- Alfonso de la Guarda