On Lost, Time is a Messy Rope by Bude

The WHH and ALT arguments are beat to death at this point, but I think both, in a way, will prove true.

Take Desmond, when Faraday knocked at the Swan's door and Desmond opened it, I believe Desmond's timeline changed. Two timelines (the one we had see Desmond live and a second in which Desmond speaks with Faraday) emerged. These timelines merged when Desmond awoke on Penny's boat.

I also believe that the Oceanic plane has traveled through multiple timelines. In one, the plane crashes on the island. In another, the plane crashes into the ocean and everyone dies. In yet another, maybe we will see the plane reach its proper destination.

Picture time as an endless rope. Typically, it is held tight with time progressing along its path. If somewhere along the way, the rope is bunched up with loops and bends, time has multiple paths. It could take a big hanging loop or a short loop or one that twists like a cockscrew. These are all different time loops. However, eventually, all these loops will wind up back on the same linear path. The loops are ALT. The linear path (an eventuality) is WHH. This why Desmond both had the conversation with Faraday and did not have the conversation with Faraday. This why Charlie is both dead and not dead. In one loop, he died. In another, he did not. In the case of death, I'm not sure which loop will "win."

Applying this to Lost, at some point, the timelines will merge into one path. There will be no doubles or iterations or clones. And there will have to be a point at which this occurs. A believe it will be with the destruction of the Island or it happened (if and) when the Bomb was detonated at the end of Season 5.