The plane scenes make no sense
So, this nutty dude is talking to an invisible man on the plane, saying crazy things like 'hey, we have the exact same briefcase', when everyone else only sees one briefcase, and NO ONE reacts? No one nudges him and says, 'hey, are you OK, buddy? You're talking to yourself out loud'?
I mean, this is just ONE of the probably THOUSANDS of scenarios, where the Narrator ABSOLUTELY should figure or find out about the situation due to outside interference of SOME sort. Wouldn't at least someone call the air hostess and ask her to check if he's OK, etc.? Wouldn't the air hostess be suspicious of that behaviour and mark him as potential threat or whatnot?
I mean, come on.. think about ALL THE IMPLICATIONS of the twist that would and SHOULD realistically destroy everything we've shown in the movie, nothing could happen the way shown because of the twist.
As I have said before, this movie LIES to the viewer and shows things DIFFERENTLY than how they happened, just to serve the twist.