I think that Due Date operates under the main premise that the viewer has never heard of Planes, Trains, and Automobiles, for if they had, they'd be wondering why they were watching the same movie with all the jokes stripped out. Due Date is, in total, neither a terrible nor an offensive film. Its problem is that it's a little too bitter, thus eliminating with surgical precision any empathy we might have for its two protagonists. It's a road trip with an obvious end in sight and somewhat unpredictable wacky hijinks in between. You could do worse, but you could do much better.
Peter Highman (Robert Downey, Jr.) is an architect who's attempting to fly out of Atlanta back home to Los Angeles to be with his wife Michelle Monaghan, who's about to give birth. But thanks to a bag mixup with a fellow traveler named Ethan Trembley (Zach Galifianakis), Peter finds himself stranded in Atlanta, placed on the national No Fly list (minor misunderstanding, of course). Ethan offers him a cross-country ride in his rental, and off we go.
The movie uses the trope of mismatched people enduring a common experience. Peter is uptight, dithering endlessly about what to name his newborn. Ethan is, well, flighty. In fact, Galifianakis seems to be playing the same character he played in the two Hangover films: childlike, maybe psychopathic and/or sociopathic, not all there. He's wildly misinformed about such things as the Grand Canyon and the Hoover Dam, but he is heading west to try to make it as an actor in Hollywood. Oh, and did I mention he's carrying the ashes of his deceased father in a coffee can to dispose of along the way? Well, there's that, too.
You and I both know that there's no way Peter and Ethan will make it from Georgia to California without any problems. But Peter has no choice - his wallet was confiscated at the airport, and his bags are on their way to LA. He has no cash and no ID. It could happen to anyone. So he's essentially at Ethan's mercy. Along the way, we learn much about the characters and what makes them tick, but whereas the earlier Planes, Trains got melancholy without getting maudlin, this one achieves no such feat.
Downey, Jr. and Galifianakis give it their best shot, and to tell the truth they're not bad. They make an okay team; it's just that it's a teaming we've seen before, and much better. Steve Martin and John Candy got into their share of situations that would never happen to a normal person, but they also ran into problems with which we could all relate; here, it's more of the former than the latter. It's as if the movie keeps daring itself to get weirder and weirder.
The final, near-fatal flaw of the movie is that it really doesn't give you anyone to root for - except of course at the end. It's a comedy, after all. But these guys do some rather nasty things to each other, and not in the oh-no-he-didn't sort of way, either; rather, in the scowling, almost hateful way. It's a little disconcerting at times. But the actors do their best, as I said, and you could do worse.
