That raises more questions than it answers though.
How did the people go back to the real world and then drag others back with them on the second plane crash?
How did Widmore find the island with his boat crew and meet up with the survivors?
The Dahrma initiative are all dead people? It seems unlikely. Was Juliet hired when she died?
It just doesn't work. It essentially destroys the consistency of the entire show.
I had the idea towards the start of this series that the outcome in the flash side-ways was all down to how well they were doing on the island (look back a page or two :lol
. It didn't hold up within one episode of me thinking it, and it still doesn't now.
The writers have said "if we reveal ALL the mysteries, they're no longer mysteries and they no longer have any function or value".
I think they made it clear that the Island is real, and the challenges and life they had was all real. Kate, Sawyer, et al flew off the island and lived a life in relative normality. Hurley and Ben ran the island and, I think we can assume, got Desmond back home.
It's that chat Hurley had "You were an excellent number two" to Ben. It suggests much further relationship between the two characters that played out beyond the "Jack arc". They had a future we didn't see. That couldn't have happened if they were all dead and went to the flash sideways world the moment Jack died.
They remained on the island and had a whole bunch of fun little Hurley and Ben adventures.
If they did that, then we also have to assume that Lapidus and the people on the plane ALSO had a further life and they flew away from the island. If they had remained, Hurley would have included them in his little secret "we had fun times" kind of chat with Ben.
The wreck at the end? It was just rounding things off with Jack dying - going right back to the beginning...