How To Make a Paper Plane.
I can't believe some stores are selling foam planes up to $2.95 USD a piece. Here are the instructions how to make a simple, yet effective, paper airplane. It really flies! (6/03/2007)

I'm not a professional origami maker, but I know how to make some things using paper. It doesn't require engineer degree or something like that, just paper and free time.
Foam airplanes costs $0.50 USD but some stores sells it with a price of $1.00 USD, Last weekend I saw it for sale with a price of $2.95 USD. I can't believe people actually purchases it for their kids. I wonder if today kids doesn't know how to make their own toys.

My paper airplane costs less than a penny, just get a paper sheet and that's it! You may use some pencil colors to make it nice but you really don't need it.
Here is the list of materials:
Paper sheet.
Scissors (optional).
Pencil colors or crayons (optional).
*** WARNING *** This project may be dangerous. Please read the disclaimer at the main page. Even paper planes can poke your eye, or you can get paper cuts. Those instructions are for educational purposes only.
1. Fold the paper sheet in half, vertically.
2. Two corners on one side needs to be folded inside. Open the sheet and fold it as shows the next photo.
3. Fold the triangle.
4. Each corner need to be folded in angle as the next photo shows.
5. The angle should not be exactly 90 degrees. Fold the other corner as the right one.
6. Almost done. We need to cut half inch on each side as the photo indicates. You don't need to use scissors, just rip it.
7. Fold the tip over each fold.
8. Fold the paper in half. The flat side of the paper without any fold goes inside. The side with all folds should be visible all the time.
9. Fold each side to make the wings.
10. Fold the other side and the paper airplane is done.
11. At this point, it may fly but you need to do some adjustments on each wing as the red circles shows. Folding each corner, small folds, makes the airplane to fly better, however, you can cut the wings as the blue lines shows to make it realistic.
Here is my paper Airplane flying inside the house. To make it fly, just throw it gently, upside down.
I do recommend to cut the wings, it makes the plane to fly nicely and wings doesn't need any adjustment. Kids may like to paint it.