Here's something that was printed on the inside of a Styrofoam egg carton lid.  The lid was flat with no indentation to add strength (like some cartons have).  It was a simple matter of using an X-Acto knife to cut out the plane.  I found a large paper clip worked fine for a nose weight was was easier to attach than pennies.  If you look carefully the main wing slots are curved to provide lift.

To make your own....do the following.

Use your right mouse button to save the pic to your hard-drive.  Resize pic to size you want and print it out.  Lay over Styrofoam and cut out plane....X-Acto knife works well...careful of your fingers.  Assemble and enjoy with your kids.  This plane will last a day or two with a typical kid.  Covering parts in clear packing tape will greatly extend their life.