People who were kids in the 1980s might remember this, maybe not, but I think The Adventures of Mark Twain should be added to the list. It was released in the UK under the title of Comet Quest. It's a Claymation film directed by Will Vinton (the guy behind the California Raisins) that focuses on Twain's attempts to reach Halley's Comet in 1910, inspired by an actual quote of Mark Twain's. I loved this film as a child and recently got it on DVD. In the film, he uses an hybrid steamboat/airship to reach said comet, while bringing Tom Sawyer, Huck Finn and Becky Thatcher along for the ride.
Funny thing is that I get a lot more out of the humor and plotline than I did as a young child, one part of it is rather grim, even from an adult's perspective. All of the segments of the movie are based off of his works, too, which is also a neat bonus.