Start with a rectangular sheet of paper
Fold the paper in half lengthwise
Unfold it
Fold the top two corners toward the center crease
Fold the new top edges toward the center again
Fold the airplane in half along the center crease
Fold down one wing
Flip it over and fold down the other wing
Adjust the wings so they are even
Flatten all creases firmly
Throw the airplane gently from the middle of the body