I'm sure many of us remember making these out of papers at home, with friends, or in school even though we may have been told not to. You fold the paper into the place, throw it forward, and it glides straight forward. Or sometimes at some weird angle if you didn't do it right. But what keeps them in the air longer than a lot of other things, and what makes them turn weird ways sometimes? Well, in addition to the downward force of gravity, a drag force caused by air acts opposing whatever direction it's moving. This doesn't affect massive objects with certain shapes as much, but light objects like paper certainly feel it's effects. If made and thrown correctly, a paper airplane will have very little air resistance in the horizontal plane, meaning it will keep moving and barely slow down. However in the vertical plane, the paper feels a much greater drag force opposing the force of gravity, keeping it in the air longer. If the plane is thrown at an angle, air resistance will act to oppose it's motion, which will point it in a different direction because of the paper's orientation.