Fact: we are explicitly told that when Desmond fails to push button = 815 crash
Season 6 pilot: The Flight Attendant gives Jack 1 bottle of Alcohol instead of the two that were shown in the "original" timeline. Season 1 pilot: Jack opens his eyes, gets up, and checks his pocket -There is only one bottle of Alcohol instead of the two that we are shown in season 1 subsequently.
The writers have claimed from the beginning that they knew where they were going with the show. To prove that they have been placing facts (like adam and eve, black and white stones etc) all along the show so that in the end when they reveal the secrets they can include these facts as part of the story to say "see we knew from the start!"
What better way to do that than to connect the "original" and "flash sideways" in the very first scene of the show? And generally whatever is revealed in the Pilots is usually supposed to be very important.
The obvious fallacy with this theory is that we are shown in LA X that the plane in fact lands safely. Or does it? The writers want us to believe that the incident (supposed to be jughead) was responsible for the "splitting" of the timeline and that now there are two concurrent timelines: the one on island post jughead and the "flash sideways". However, there is no proof that the "flash sideways" started happening as soon as the Jughead incident. "Flash Sideways" could have happened anytime (haha), and only now they are being revealed to us. Is it not possible that the timeline in fact split when Desmond failed to push the button? That would explain why Jack wakes up with one instead of two bottles of Alcohol in the "original timeline".
PS: Newbie alert :) and thanks if you got this far...