Most of the frustration with model building is that you really can't play around with your finished model. It's for display as opposed to just "play". This can be discouraging to young builders.
Enter the rubber band plane. This thing is easy to make and it flies. It is designed to be played with, and it can be a good day project with a younger child interested in model building, aviation, or engineering. Any kid would likely be interested, as you're building a little plane that really does fly. It's always a hit with my nieces.
Common household materials can be used.
I find kits are much easier for everyone involved.
“It's always a hit with my nieces.”
Some of the nuts and bolts of a truly DIY rubber band plane.