The evil Dr Destructo is building a fleet of ships, and is about to sally forth and conquer the world. Luckily for us, the airforce have got wind of his plans and are sending a fleet of planes to destroy the ships before they embark.
One or two players fly their craft over the ships, shooting down as many of the defending planes as possible. Shooting a defender causes it to crash down to the ship's surface - damanging the hull on contact. Cause enough damage and the ship sinks, allowing the player to progress to the next vessel.
Although the action is repetitive, it's absurd enough to be enjoyable - especially with two players.