Agree with what's been said in the other answer (iandotkelly), but also I consider a major factor to be mood. The whole sequence is designed to give that sense of the magnitude of their (his) accomplishment, and heighten his fear and expectation as he makes it through immigration and then customs and finally freedom. Plus there is a general sense of a dream or waking from a dream as the camera tracks his movement through the airport.
Plus anyone who's ever travelled on one of those long flights knows the feeling of slight zombification you get from landing until you're finally home. It actually conveys that feeling really well! Though I doubt this was an aim of the filmmakers. heh.