The speculation continues, as to the cause of what shut down all engines. As was suggested earlier in the thread, only after a protracted length of time has passed and a thorough investigation concluded, will the true cause be known. Yet that conclusion will not be the true root cause, as a single circumstance or reason, mechanical or human related, is never to blame. Rather, a complex, systemic series of factors will more than likely be proven to have caused the engine failures. For more on this subject see[How Complex Systems Fail - Richard Cook, MD -]