Sun puts her trust in Jack, communicates by writing

Near the beach camp, Jack approaches Sun who is sitting alone next to a fire on the beach. Jack hands her a notepad, telling her that she might be able to write in English even though she can't speak. It turns out he was right.  Jack says that he went back to her garden to see if Locke was there, which he wasn't, but he did find a stubborn tomato that apparently didn't know it was supposed to die.

Using the notepad, Sun apologizes and tells Jack that Locke said he has Jin. She says that she didn't go with Locke because she doesn't trust him. She says that she does trust Jack, who says that if she goes with them, he promises that he'll her and Jin on the plane and get them off the island.

So it seems that Jack is either lying to Sun, or he's not onboard with Richard's destroying the plane plan. Either way, the conflict should get interesting.