Desmond is on the boat from what I've read. It's likely the boat he was sailing around the world in... I dunno.
We'll likely find out a potential reason why their plane crashed, I'm guessing they'll give us something to make us think that is the reason while it's just a ruse.
I wonder if it will end with something happening to Walt, while Locke smashes the computer causing the numbers to roll like crazy and the BAM... another plane crashes.
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