Lots of good points coming out on this tread. The lack of children in the town would make the abdution of the two tailie kids, Walt and the attempt at taking Aaron make more sense.
As for expectiong the plane crash... We know that there had already been a small plane crash, a sail boat, a slave ship, a group of scientist and a hot air ballon. If they didn't have some kind of plan for new arrivals I would be surprised.
I don't think they knew it was coming but, I do think they knew it was possible and had plans in place. The reaction they had when the Swan hatch blew was as if they had been through it before. Just like when the earthquake hit. They delt with the situation fairly calmly and then went to work.

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