[Gay State Conservative]

The plane stalled. Could be pilot error, mechanical malfunction, or load shift, but nothing popped out the back end.

IIRC the 747 is designed with some sort of barrier or "bulkhead" at the rear of the plane near,but not right at,the "tail".

It's my understanding that when that "bulkhead" is compromised in any way you've got a big problem.

[DuncanWaring]

Japan Airlines Flight 123 crashed in 1985 due to an aft pressure bulkhead failure which destroyed the hydraulic systems.

https://en.wikipedia.org/wiki/Japan_Airlines_Flight_123