Through the history of flight, the number of lifting surfaces has been fiddled with in an effort to hoist more weight into the sky. The biplane was found early to provide a good tradeoff of lift to additional structure weight, and it has remained in production for more than a hundred years.
The Rules and Regs
For entry in this mission, the aircraft must have two stationary wings to provide lift. All eras are welcome, from the Wright Flyer to the Antonov An-2 Colt, in any scale.