@BenFranklin: Agreed. Although you have to realize that the plane crash was just one of the events of that episode.
Considering that the cost of showing the entire plane crash would be very expensive (the pilot with plane crash of the tv show Lost costed somewhere between 10 and 14 million dollars) i think the producers went with a more cost effective solution: an airplane chair, some rubble and a greenscreen to generate a CGI plane crash in the background.