I believe that when Jack died in the OT next to Vincent in the Bamboo fields that when he closed his eyes he woke up on the plane going to LAX. He was dead in the FST and it was a sort of purgatory for everyone. Thats not what this blog is about if you want to debate that or offer your own points see my previous blog.
However, I found one line very fascinating. Right when we saw the FST for the first time. The very first line was spoken by Rose who said "You can let go now"
I believe this was a nice way to sum up the FST. It was all about getting Jack to "let go" and come to terms with his life and all that happened in it. It really became that way for all of the survivors. The ones that were able to "let go" were in the church at the end. Led by Christian Shephard into the light.
(PS I am so glad they brought Christian back because I was really hoping they didnt just end it with saying MIB was Christian the whole time)