I originally saw Donnie Darko off Matt Allison's recommendation, and since then have introduced numerous people to the joys therein. However, neither I nor any of those I've seen Donnie Darko with have been able to explain the movie in a way that MAKES SENSE! I sat through several post-viewing bull sessions last year, but no one seemed to be able to come up with a logical explanation fo the plot. I wanted to post the following to perhaps encourage others who know or believe they know how to adequately explain the plot to do so.
Recently, a friend of mine sent me the supposed contents of the fateful "The Philosophy of Time Travel" book that came into Donnie's possession (I think these may have also been in the extras on the DVD version of DD, but here's the source website). I wanted to respond to the contents here. The Philosophy of Time Travel (POTT) is hugely succesful in both explaining the movie, and supporting my own interpretation of the movie in a self-satisfying way.
Prior to reading the POTT copy my friend sent me, I would have said the biggest loose ends in the movie (those ends that prevented the plot from making logical sense), were these:
1. We sort of realize that Donnie has to fix the loose ends in the tangent universe in which he's trapped, so we guess that he realizes that the jet engine that nearly killed him when the whole thing started comes from the plane on which his mom and sister are riding in. The loose end for us is: How does Donnie cause the plane to fly near enough to the black hole to for the engine to break off and go back in time? The book provides an explanation for this is noting that the Living Receiver often has super powers. Remember Donnie sticking the axe into the bronze statue's head? Remember what he says when Gretchen tells him that his name sounds like a super hero or something? POTT clears this up.
2. What POTT doesn't clear up is WHY THE FRICK THE JET ENGINE COMES THROUGH THE ROOF AGAIN AT THE END OF THE MOVIE?!!!?! It's like the director wanted to present this difficult yet coherent plotline about time travel, then, after making everything work out just right, for absolutely no reason, tosses in a totally random and logically destructive plot device that kills the protagonist! POTT is, as far as I can tell, no help at all on this point.
My theory is that Donnie Darko can make coherent sense--but only apart from the redundant jet engine. The redundant jet engine is the paradox-maker. I propose that an account of the movie that can incorporate and explain the redundant engine will make the whole film make sense. In fact, the Redundant Engine Paradox (henceforth REP) is the key to whole film. If you can explain the REP, then you can explain everything. I believe have identified the necessary conditions for the coherence of Donnie Darko, without supplying the answer myself.
Just kidding--here is my initial attempt at solving REP:
Donnie realizes how tangent universes work towards the end of the one he's in, and too late to accomplish what must be done to fix things. However, because he's a bright kid, and because of his knowledge about how tangent universes work, he figures out how to spawn another tangent universe (T2) before the one he's in (T1) implodes. So when he uses his superpowers to break the jet engine off his mom/sister's plane and send it into the black hole back in time, he's not fixing T1. Instead, he's initiating T2 to buy him time to fix the problem.
Of course, you will now ask why the FRICK does he allow the jet engine to kill him in the newly spawned T2? This is the sheer genius of this account: Donnie knows that the memories of T1 will vanish upon the termination of T1, so even if he can succesfully jump everybody into T2 before T1 implodes, it won't matter because he won't remember what he's learned in T1 (Donnie can't be sure that Frank will be there to help him out this time) and therefore, he won't be able to save them in T2!
Unless he dies in T2!!!!!
Donnie knows that the only way he can be sure to find out the truth about their status in time-limited T2, once they leave T1, is if he dies. Remember from POTT: those who die in tangent universes have unique power. Upon his death, Donnie will learn the truth, and so he counts on his own ability to figure things out anew in T2.
He knows it will be harder to directly accomplish things in T2, since he'll be dead, and likely grossly so. But he knows that he doesn't have to. If he can't find a way to effectually influence someone in T2 to fix things, all he has to do is to get someone to spawn T3. If Donnie plays his cards right, he can keep everyone jumping from tangent universe to tangent universe until he gets his ducks in a row and closes the tangent universe off for good.
(A good way for Donnie to acheive final success would be--somewhere down the T-line--to figure out how to make sure that he himself dies late in a tangent universe. If he could ensure that that would happen, then Donnie-dead would be able to guide Donnie-live in the earlier part of the tangent universe to do the things he must do to close off the causal loops and fix things, and then kill himself towards the end--to make sure Donnie-dead would be able to go back to guide him earlier in that tangent universe.)
OK-that's all I have for now. But it's the first explanation that I've seen that adequately makes sense of the Redundant Engine Paradox.