Import Files to another?

I know its possible but i have no idea how to even go about it.

I am needing to Add an Airplane to a file with a terrain scene in many deifferent times.

Our class project was to make a plane, each one of us. Then we needed to bring them all together in one scene for a dogfight.

But i have no idea how to get the planes into the Scene.

Any Ideas or perfect explanations on how to do this would be very much appreciated!


Shift+F1 to append the objects