Planes, Trains and Automobiles movie review (1987) | Roger Ebert:

One night a few years after "Planes, Trains and Automobiles" was released, I came upon John Candy (1950-1994) sitting all by himself in a hotel bar in New York, smoking and drinking, and we talked for a while. We were going to be on the same TV show the next day. He was depressed. People loved him, but he didn't seem to know that, or it wasn't enough. He was a sweet guy and nobody had a word to say against him, but he was down on himself. All he wanted to do was make people laugh, but sometimes he tried too hard, and he hated himself for doing that in some of his movies. I thought of Del. There is so much truth in the role that it transforms the whole movie. Hughes knew it, and captured it again in "Only the Lonely" (1991). And Steve Martin knew it, and played straight to it.

The movies that last, the ones we return to, don’t always have lofty themes or Byzantine complexities. Sometimes they last because they are arrows straight to the heart. When Neal unleashes that tirade in the motel room and Del’s face saddens, he says, “Oh. I see.” It is a moment that not only defines Del’s life, but is a turning point in Neal’s, because he also is a lonely soul, and too well organized to know it. Strange, how much poignancy creeps into this comedy, and only becomes stronger while we’re laughing.