Problem with local axes

I'm now really tired of trying to make my things work. Here's the stuff : I want to make a plane and so i taked some script. For this script to work, the local z axis of my plane must be upward and the local x axis toward the nose of the plane. I undertsand this part. The problem is SL builder works like ****. How am I suppose to give those precise axis now that i have tranformed and rotated my plane so many times. I've tried to put a newly created cube (with the default local axis, which are right) as root primitive, but it doesn't seem to work. All help will be appreciated. Thanks.