Leaving a trail

Hey,

Doing a little animation where a plane flies over a map and I want the plane to leave a trail (a line) behind it.

I've searched the forums and tried a few things like Echo, Generate Stroke etc. to try and do this but can't make it work. I figure it must be pretty simple but I just don't have the technique.

The plane is a layer and I'm moving it around using keyframes on position, scale and rotation. The animation looks fine for what I want to do but I just need to figure out how to leave a line behind the plane. Hope that makes sense, any help appreciated.