Keg, you say
'threats' are supposed to be external to the crew
. Why "external" to the crew?
I always thought that a threat was anything that could result in an error being made. So if a crew member is tired or suffers from fatigue, there is the possibility he may make an error. The crew member may be suffering stress from personal problems such as financial, marital, death in the family etc,. this could also be identified as a threat which could lead to an error being made.
One now has to look at the types of possible errors resulting from fatigue and stress. Poor decision making is the most obvious. When you are tired or stressed your decision making is usually flawed. Failure to monitor or challenge the other crewmember during times of high workload. Decreased motivation resulting in possible loss of situation awareness.
Then, as you have correctly pointed out, one must be able to manage this threat. Fatigue and stress can be managed to a certain extent by the individual but may have to be addressed at an organisational level as well.
An airline (I think it was Continental) in the States had a good saying about Threat and Error Management:
“Threat Management is managing the future.”
“Error Management is managing the past”
I think the problem with a lot of Human Factors and Crew Resource Management courses these days is that they are too complicated with models and theory. What's needed is a practical HF/CRM course with real life scenarios,videos and a clear definition of the behavioural markers experienced everyday in aviation that mere mortal aircrew can relate to and understand.