So, what kind of rosters are the NWA pilots on? Anything like the EU OPS Subpart Q with up to 60 hour weekly duty? 13-15 Hr days?
I've had my copilot nod off on a 1/2 hr flight once, and after I took a look at his roster at the time, I was not surprised.
We don't fall asleep at the controls without a reason, and we don't discuss/fight, whatever, way past TOD.