Yeah, that's one of the most mocked things in the movie. I also like that they successfully rebel using those jets 1,000 years later, after losing the war in 9 minutes or something when they were first invaded.
I've read Final Blackout, which is supposed to be one of Hubbard's best books, and I didn't like it. It's a military post apocalyptic novel that has some decent battle scenes, but I thought it was to dour and pro-authoritarian.
I own Typewriter In the Sky and Fear, which are supposed to be two of his other better books. Fear, in particular, has a decent reputation. If those turn out to be worthwhile then I'll probably read To the Stars/aka Return to Tomorrow, which is an early example of a story that makes use of the concept of the passage of time at relativistic speeds (so that's one at least that does have science in it). That's probably it for the Hubbard I'd be interested in reading. I'm never reading Battlefield Earth, which is longer than all four of those other books put together and is not actually an important work of SF at all. And I'm REALLY never reading the Mission Earth series (the books he wrote after B.E.), which combined is substantially longer than B.E. Earth and which has an even worse reputation. Scientologist block voting got the first Mission Earth book nominated for a Hugo but in the final vote it finished below "No Award."