Cost, Durability, and Safety

Cost: $30 - $40, add on kits could have specific parts and cost $10 - 20

Durability: As with all plane kits, durability would be the biggest issue. Because of this, I envision the parts being made of a high density foam with plastic inserts for the pins and slots. This would allow the plane to take numerous hits without becoming un-flyable. However, over time the pieces would accrue many dents and gouges.

Safety: The planes might hurt if thrown very hard at another child, but the intended age range is 8 - 15, so hopefully the children will know enough not to do that.