A critical observation or two about the premiere's parallel universe split time line events. The story line clearly states that Juliet did in fact detonate the H-bomb. Instead of vaporizing herself, killing everyone in the vicinity, and having radioactive fallout destroying everything else on the island, we are lead to believe: the island moved forward to 2007, to sync up with the 316 crew; Juliet did not die in the explosion; everyone was in their pre-explosion condition (except for ringing ears).
The apparent explosion was similar to the Desmond fail safe key explosion, which is the debris crater where the 1977ers found themselves. If one is going to be consistent with the mythology within the show, this type of EM explosion, moving the Island time would mean that there would not be one "flashsideways," but at least four parallel universes: 1) the original 2004 time line; 2) the Desmond fail safe key explosion; 3) the Locke turning the FDW and moving the island; and 4) Juliet exploding Jughead. We are only seeing the New 2004 815 universe compared to the Old 2007 815 universe. It also comes to mind that all the parallel universes (the flash backs, flash forwards, past off-island events) are immaterial filler to the main core story line. It does not take five seasons of jumbled editing to show us that the lives of the 815ers would not have been much different if Flight 815 did not crash.
And this episode puts into doubt the statement that Desmond's failure to input the Numbers caused the original crash of Flight 815. I think the new Flight 815 was also going to crash on the Island - - - if it had a dead body on board. Jack Shepard's body was not in the cargo bay of the plane. The turbulence was caused by Charlie choking down heroin in the lav. If Charlie had died on the plane, then the island's tenacles would have sensed a dead person and grabbed the plane toward it. This could be the protocol of the island (Jacob) bringing people to the island (as a station towards the afterlife). This could also fill a need for Jacob and/or MIB to replenish their inventory of the dead so they could use, manipulate or control the dead bodies as part of their personal battle.
The New 815 flight is mostly a throw-a-way look at the lives the characters would have absent the crash in the alternative universe where individual free will decisions are like a roll of the dice on the board of life: it was a 50-50 chance that Boone would have convinced Shannon to leave her boyfriend - - - in the first roll, it worked; the second roll it did not. Same goes for Jack getting his father's coffin on the plane: the first attendant said it could not get on the plane but Jack convinced him it had to be done; the second time the coffin was lost in the terminal and it never got into the cargo bay. The writers had cornered themselves in the time travel problem of paradox. The solution was to create parallel universes which negate any paradox issues in the original time line. So the New 815 time line should have no bearing on the original 815ers who have returned to 2007 (main story line).