I had it figured out after the first show of the first season. They were simply dead which is ultimately what happened. It just took them a lot of years to say so. The ending was a cop-out by the writers. While it was a "sweet" ending it left me very unsatisfied. You can read all the deep dark meanings in it you want, but they simply were dead. So what happened to the pilot and the other guy in the plane who wasn't at the "funeral?"