One news report mentions an observer in Owen Valley, California who noted flashes as the shuttle passed overhead which raises the possibility that pieces/tiles could have started coming off at that point.
Any such early pieces that came off would be important to the investigation, but what are the odds of finding them when they could have landed in snow, forest, desert, mountain or water after the winds have blown them off course?
The apparent intense fragmentation over a wide area makes it unlikely that all the pieces in the main debris field will be recovered, which will add to the difficulty of identifying by elimination which pieces came off first.
If a substantial span of the the left wing failed, the right wing would end up acting almost as a rudder and the left fuselage side would be exposed to beyond design aerodynamic forces at M18
