This plane failed to respond to a call from Denver Center when it attempted a handoff to Minneapolis. It overflew MSP, its intended destination at FL 370, never making any attempt to descend. The Air Force had been contacted but apparently never scrambled. Over 100 miles after overflying MSP, ATC was finally able to contact them and get the plane turned around to MSP, where it landed over one hour late. All that I have stated above is verbatim from ABC news which featured this story prominently this evening.
This plane was out of contact with ATC for over an hour! Not good! The CVR will record the final 30 minutes if IIRC. So the alleged argument may not be recorded... perhaps any conversation to come up with a cover story may be recorded.
It is hard to figure anything other than sleeping pilots as the cause of this "incident". Between this and the DL flight landing on the taxiway at ATL, it has not been a good couple of days for the DL/NW cockpit brethren.
Again, the concentration should be on what we can collectively learn from this.