I have used wings 3d before its very easy to use and best of all FREE! I use it some times in designing aircraft for a flight sim called X-Plane. I know there are good ones out there like AC3D(
www.ac3d.org), Blender(
www.blender.org/), and GMax(
www.autodesk.com/gmax ).You can find plugins on the net that will convert models made in these apps to 3DS MAX. AC3D has an converter built in the last time I checked.
Here are some expamples of a fantasy senery project made in AC3D
This aircraft is unfinished but many parts of it was built in Ac3d
Here is a example of a A340 cockpit in Blender.
