So contrary to my optimistic earlier assessment, in the event that it is found that the Ethiopian 787 fire was caused by a spontaneous ELT battery meltdown, had the same incident occurred in flight, one would expect:
1. Numerous passengers and cabin crew to die of asphyxia and/or cyanide poisoning, although flight crew possibly protected by crew oxygen.
2. They will need to try to get on the ground in single digit minutes because otherwise there will be catastrophic structural failure driven by merely heat, e.g. the tail will fall off...
3. But thery won't make it because the skin itself will burn like a firework in the airflow round the plane..