From Miko "Ohhh, I just thought of another one that didn't occur to me. At "we are starting at the beginning of this season" -- does that mean we're using flash-sideways lives and then they crash?
So, to be specific: Is Ben still leader of the Island, and he just took a random trip and is now flying back -- or is Ben a European history teacher who's never even heard of the Island (maybe)?"
When they are on the plane, they are living their side ways lives. Once they crash that reality is gone. Ben will have to remember that he is leader or was leader as the case may be. Remember that things will occur slowly, and how he begins to remember is up to Miko. Of course interaction with each other will help that. He would have stronger feelings of recognition with Richard and John even more with Jacob. His feelings toward John would probably be mixed based on their past relationships, but that's up to Miko and how she chooses to play him.
There won't be any side-ways flashes. Only dreams and flash backs. In your dreams the characters could dream of what might have been had they not been on the island.