One of my fun outreach programs is an engineering club at a local high school, Sheldon. We have built robots, rockets, and radios. Now students are building remote control airplanes. These are relatively cheap to build as they are made from a couple sheets of foamcore. I did my own workshop on building planes for a Lane ESD summer camp for kids through the Eugene MakerSpace two years ago. Planes are great to make because they are fun and they require learning about wings, lift, drag, centers of pressure and centers of gravity.
And here is a plane in flight: