After having a bout of one-upmanship, Tom Sawyer, Huck Finn, and Becky Thatcher sneak aboard an airship piloted by Mark Twain in an attempt to become famous aeronauts. Upon discovery, they find that Mark Twain intends to pilot the airship to meet Halley's Comet. Worried that this goal will end in their deaths, the trio learn to fly the ship while conspiring to sabotage the voyage.