The original crash we haven't seen/trauma therapy theory by lostie8

I believe there is an original crash that we have not seen yet. All of the Losties were in this crash which was caused by a bomb. Before, during and after the crash many things happened that created a huge amount of survivors guilt, anger and rage.

So, all of the Losties were sent to an institution to use a newly developed virtual reality therapy - where they get to recreate scenarios that are bothering them. The therapy "game" is played both on and off the island, to allow them to get full closure and work in conjunction with each other.

This is why in the flashbacks (as well as other off-island experiences) we see things related to a crash - Locke flying through the air, Kate robbing a bank for an airplane, endless car crashes etc. It also explains all of the repeated "bomb/deactivation" issues. Someone at the institution they are in (probably part of the Hanso foundation) is leading all of the efforts. It also explains all the game references - plus probably someone was playing a game on the flight during the original crash.

The Smoke Monster is actually a symbolic representation of the destruction that the crash caused and continues to cause in the survivors life. Some of those in the virtual game are the staff/Doctors from the institution.

So, during the original crash - Claire lost her baby in the crash(and all the survivors are angered that none of the babies were able to be saved, but Charlie and Kate feel exceptionally guilty about her sons loss), Frank is feeling guilty about not being the pilot that should have been flying the flight and is in the game to redeem himself by helping the others now, Sun survived the crash, but Jin did not - and she's trying to figure out how to get over it, because they'd had a fight prior to it, Hurley feels guilty about the money he took from the airline after the crash and thinks he caused it because he was a bad luck charm... etc., etc., etc.