There's gonna be 2 realities. The one on the island after the bomb going off (no idea how almost everyone survives), and an alternate timeline where the plane did not go down.
there was no plane, man, don't you get it?? there was no plane, man. they just want you to think there was a plane but there was no plane. if you're thinking about the plane then you're not thinking about the helicopter, man. you need to focus on the facts bros, there isn't, and never was, a plane.