Things You'll Need
Instructions
 
Cut the balsa wood sheet in half with the X-Acto knife, so that you have two 8-by-3-inch sheets. Use the straight edge to ensure you get a clean cut. 
Cut one of the sheets in half again, so that you have two 8-by-1 1/2-inch sheets and one 8-by-3-inch sheet. 
Round the corners of one 8-by-1 1/2-inch sheet using the X-Acto. This piece will be your wing. 
Cut a 1-by-2 1/2-inch piece out of the remaining 8-by-3-inch sheet and round the edges. The small piece will be the plane's elevator. 
Cut down the remaining 8-by-3-inch balsa sheet to 7-by-2 inches. 
Draw the silhouette of a plane on the 7-by-2-inch balsa sheet. Make the rudder 2 inches high in the back and about 1 1/2 inches wide where the rudder meets the fuselage. Make the plane's fuselage 7 inches long and about 1 inch high overall. 
Cut out the plane's silhouette. 
Round the nose of the plane with the X-Acto. 
Make a 1/2-inch notch in the plane's tail, horizontal with respect to the fuselage. Don't make the notch too thick. It has to hold the elevator tightly. 
Cut a 1/2-inch notch in the front of the plane's elevator. Be sure the notch is centered and no more than 1/16-inch wide. 
Measure 2 1/2 inches back from the plane's nose and cut a 1 1/2-inch long slit in the fuselage, no more than 1/16-inch wide. This will hold the wing. 
Assemble the plane by inserting the elevator and the wing into the notches you made in the fuselage. 
Tape a dime to the plane's nose for weight.