In the paper airplane activity students select and build one of five different paper airplane designs and test them for distance and for time aloft. Part of this activity is designed to explore NASA developed software, FoilSim, with respect to the lift of an airfoil and the surface area of a wing.
If students are not able to calculate geometric areas, they could make a duplicate plane, cut off the wings, and lay the wings onto measured grids or pieces of graph paper and count the total squares covered, estimating partial squares.
A variation of this technique that eliminates a duplicate plane and cutting wings is to draw or trace a grid on a blank transparency with a sharpie marker and then hold the clear grid over the wings to count squares covered.
The cut off part should be tucked on the inside of the plane when it is refolded in order to keep mass constant. You might ask the class to provide an explanation for doing this.