Interestingly enough, I read yesterday at Mo Ryan's column (http://featuresblogs.chicagotribune.com/entertainment_tv/2010/05/lost-abc-finale.html) that the images of the crashed plane at the very end of the show that was key or a lot of people interpreting that the whole show was in purgatory weren't even added by Carleton and Cuse. They were added by an ABC executive and were meant only as a "visual aid to allow the viewer to decompress before heading into the news." Mo Ryan is the television critic for the Chicago Tribune.

There's a little more to the ABC Exec's quote at the link.