OK, I just had the idea that everyone on the plane was serving as someone's proxy.
Sayid, him being handcuffed and all, seemed like he was Kate's but that doesn't make sense because Kate was there. Some people think Kate was pregnant, so she'd be Claire's. Locke was Jack's dad's and Hurley was Charlie's because of the guitar case. I can't think of any more. The thing is, if that's true, how did they get this idea to be proxies? Did it happen by chance or did Ben or Eloise Hawkins tell them to?

P.S. What was with the Middle Eastern man on the flight?