There's something bothering me about the alternative timeline.If you wanna read, please pay attention, because it's complicated.
1. Ok. A common time travel theory is that when someone goes back in time, they actually go back to an alternative universe's past, so they can do whatever the hell they want there, because it won't change a thing in their universe. So: Person A lives in Universe 1. A wants to go back in time to change event X. When A travels back, he/she actually goes to Universe 2. There, A prevents event X. So, in Universe 2, event X never happens, and Universe 2's timeline is different from Universe 1, which remains UNALTERED.
2. The problem is: HOW DID THEY MANAGE TO CHANGE EVENT PLANE-CRASH IN UNIVERSE 2?
One could say: Oh, 77's Losties actually went to 1977 of Universe 2 and set off the Jughead there. So now in Universe 2 Oceanic 815 never crashes. But if this is the case, 77's Losties never went to THEIR Universe's 1977 (Universe 1's 1977). Because if they did, they would change Universe's 1 timeline, which would fall on WHH (so they would not change it). So, they HAD to be on Universe 2. But WAIT! In 2007 of Universe 1, Christian shows a picture of 1977 to Sun. How can this picture exist in Universe 1 if the Losties were in Universe 2? Simple. They had to be in Universe 1, damn it! So how could they create a Universe 2, if they were always in 1? If they blew up the jughead in Universe 1, WHH applies and then why would this create an alternative timeline?