As Desmond Goes, So Go The Rest by tez360

Desmond Hume has often been the forerunner of major paradigm shifts. When he turned the failsafe key, the Swan energy hurled his consciousness back in time, allowing him to reexperience his past but with the knowledge he'd gained in the future. (Not knowing anything about time travel, he didn't have a lot of luck altering things.)

The conflict lies between destiny and free will. Desmond was told (by Mrs. Hawking) that the universe course-corrects. He knew that Charlie was doomed to die. But Charlie is the perfect example of Jacob's 'free will' mantra: yes, certain things are meant to happen, but we can choose the MANNER in which they happen.

Widmore and Hawking knew that Daniel was meant to die, but they did more than allow it to happen---they went out of their way to facilitate it. Why? I think they facilitated Daniel's death because a) they knew the death was inevitable and b) they wanted his death to MEAN something---his death serves an as-yet-unknown purpose that would be foiled if Daniel isn't shot by Eloise.

Because Daniel is always going to die. Charlie was always going to die. Shannon, Boone, Eko, Ana-Lucia---Jack et al think they can save the passengers of 815, but they're only half correct. If they stop the plane crash, the passengers won't die on the Island---they'll just end up dying in the 'real world'. Charlie would OD in the plane bathroom, never knowing love with Claire, fatherhood with Aaron, or true friendship with Desmond, Hurley, and the rest. Daniel would never be healed and would waste away, never knowing Charlotte; Charlotte would die of a random brain hemhorrage, never knowing Daniel, never coming home to the Island. Michael would die a lesser death than the one he had saving his friends. Desmond Hume might die on his global trip, as the Island would have no reason to 'send' for him.

I think the Losties will flash back to the plane, memories intact, and the plane will land at LAX. But when they see that their friends die anyway (but without the healing/maturation they gained on the Island), they'll get Charles and Eloise to help them undo their undoing of the past.

Free will means accepting your destiny on your own terms.