World 2-Airship (Super Mario 3D Land)
From the Super Mario Wiki
Mario starts out landing on an Airship, near three Rocket Engines and a tightrope that connects it to another Airship. A little further beyond, there is a flying Bill Blaster that shoots Bullet Bills toward the rope. On the next ship, there are three Bill Blasters and a Warp Box; following that is a third Airship with a Rocky Wrench. The flying Bill Blaster following this ship shoots Tail Bullet Bills. On the fourth and final Airship, Mario must enter a Warp Pipe to battle Boom Boom. After defeating him, another Warp Pipe will appear, leading Mario to the Airship with the Goal Pole.