Allen, I don't know how much you've been watching of Lost but I think that you may be confused about the planes. The wreckage on the beach is from Oceanic Flight 815, which broke up over the island in the original pilot. The plane that Frank, Miles, Richard and the rest took off in was Aljira Flight 316, which was the plane that the Oceanic 6 (or is it Oceanic 5 without Aaron?) used to return to the Island during season 5. That plane landed on the Other's runway pretty much in one piece. As for the plane that Jack saw at the end I'm assuming that it was the Aljira plane successfully taking Frank, Richard, Miles, Kate, Claire and Sawyer back to the real world.