Facts and Conclusions
If you take the point in time where transponders shut off as t=0, or corresponding location as origin point, a few results can be arrived at:
1. Lack of debris on sea surface in the immediate vicinity of origin point lead us to believe that the aircraft did not structurally disintegrate, either due to aerodynamic forces or through explosives .
2. Lack of IR signature confirmation by US SBIRS (Infra red spotting satellite system) also lends credence to the result that the aircraft did not explode in air at origin point.
3. Suicide theory can also be laid to rest because a pilot intent on committing suicide will not linger around in air and in fact will try to head down right away after turning off transponders leading to debris field around origin point.
4. However, since we know as a fact that the aircraft eventually crashed, it leads us to believe that the aircraft was severely impaired at t=0, even if it was structurally intact. Whatever happened around t=0 was catastrophic enough to eventually bring the aircraft down. It not only took out communication ability of the pilots but a lot more than that.
5. A set of pilots finding themselves in a catastrophic situation are highly likely to look for a landing strip ASAP. Given that they have likely lost their navigational ability as well (most likely), at night, they are going to head for nearest land, wherever they might think it is.
6. If we take it as a fact from Malaysian authorities that the aircraft tried to turn around, it could be an indication that the pilots were in trouble and wanted to find land in haste.
7. Malaysian authorities claimed in the beginning (perhaps even now) that they lost radar contact at 2:40AM, more than an hour after t=0, if that is true then they were tracking an aircraft in huge trouble looking to land somewhere or anywhere. But it provides a radius of around one hour flying time from origin point to search for.
8. Regarding US SBIRS lack of IR signature, it could depend on what their system is optimized to detect. A missile launch is sustained bright fire, an aircraft crashing in a fireball is short term quick burning fire. SBIRS probably accurately confirm that the aircraft did not explode in air, however, will it also accurately confirm that it did not burn under jungle canopy for a short time?.