Thing is that at this point there is no evidence that the plane crashed: we don't have reliable radar data, no debris, no sightings... nothing. How can they be so sure that it went down straight into the ocean
There was nothing but ocean and planes tend to go down when they run out of fuel. Whether it went straight down or at an angle makes no difference.
If you are hinting at the possibility it ditched mostly intact, no passenger plane ever ditched intact on an ocean to my knowledge (lakes and rivers is something else), especially not an ocean as rough as the one where it went down. You'd also need to explain how the crew would be able to do the impossible by doing a successful ditching but were unable to prevent the plane from flying 1000s of miles of course for the previous 6+ hours.
As it stands now, the most likely explanation IMO is still pilot suicide or something similar to Helios flight 522:
http://en.wikipedia.org/wiki/Helios_Airways_Flight_522WHich also flew on for many hours with everyone on board unconscious /dead (except possibly one crew member).
The only thing clearly different here is that transponder and other comms were disabled, which could easily be explained by an electrical fire which would be the underlying cause for the oxygen deprivation/incapacitation of the crew.
Whatever happened, if that plane was ever anywhere near the places that the satellite data points to, there is no feasible way people onboard could still be alive.
