LEGO set 30421, titled "Skybound Plane," is a 30 piece Ninjago polybag set released in 2016. It features a small, pirate-themed plane with a cockpit for one minifigure, and includes unique elements like a ship's wheel (used as a propeller) and an anchor (used as a tail). The set also includes a minifigure of Bucko, a sky pirate, and some bottle pieces. 
 
Here's a more detailed breakdown:
- Theme: Ninjago Skybound. 
 - Minifigure: Bucko, a sky pirate. 
 - Pieces: 30. 
 - Unique elements: Ship's wheel, anchor, bottle pieces. 
 - Design: The plane's design leans more towards a pirate theme than a Ninjago theme, with the wheel and anchor elements contributing to this aesthetic. 
 - Designer: Michael Knap and Nick Vás
 - Other details: It was a polybag set, likely found at a Legoland Discovery Center, and is an original build.