[SMEDLEYBUTLER]

Could have been caused by a number of failures: metal fatigue, APU failure while spooling up, loss of tiles, structural failure, etc. Telemetry will hold the key if the FDRs were destroyed.

[Rockitz]

Yes, I'm sure the fault tree will have many branches and the failure investigation will cost many millions of dollars. Look for Analex and SAIC among others to get rich on the failure investigation.