Another idea that I found through Pinterest and probably the most entertaining so far, is the straw plane (original source here). It is so simple and yet it really does fly better than any paper plane that I've ever seen. It's surprisingly robust too considering how many times its flown into walls/doors.
Riley had a blast with it and we spent a lot of time flying it up and down the hallway and seeing how far it could go.
Joining in here.