What can I build in under 3 days?

I am doing a school project and I can only use things you can find around the house without buying anything. We are learning about flight. Our project is we have to build something that flies for at least 3 seconds. Also you need to have string attached so you can run and let it fly, kind of like a kite. ( you are not allowed to build kites, you have to be creative) We have only 3 days to build our project. So what kind of flying contraption can I build in under 3 days?