According to numerous accounts in the last hour -- AP here, Reuters here, WSJ here -- the current story from the Northwest flight crew that forgot to land in Minneapolis is that they were so absorbed in using laptops in the cockpit that they neglected to talk with air traffic controllers for more than an hour and didn't get around to descending.
I hate to say this about people with enough other problems already, but: that's simply impossible to believe.
Flying an airplane is different from driving a car, in that it doesn't take constant second-by-second attention to the mechanics of where you're going and how you're handling the controls. If you type out a text message while you're driving a car, you really are putting yourself and others in danger. But if you take a minute in an airplane to check a detail of the routing, or a weather report, or anything else that comes up, in most phases of flight nothing bad is going to happen. The plane will cruise along with its autopilot, and most of the time no other planes are anywhere nearby. (Obviously this doesn't apply in takeoff and landing, in busy airspace, etc.)
That's why some of the stories tut-tutting the pilots for breaking company rules by opening laptops during flight are beside the point. That's a for-form's-sake only rule whose violation may be"wrong" but is not intrinsically dangerous.
The difficulty for the pilots is that the version of the story they're resisting -- that they simply fell asleep -- is less damning for them than any alternative version. If they fell asleep, that's bad, but they could argue some kind of force majeure. But if their "heated conversation" (previous story) or intense laptop use (current story) kept them from remembering their most elemental responsibility as pilots, that really is beyond the pale. The closest comparison would be, say, to an operating-room team that got so interested in watching a football game on TV that they sliced open a patient but forgot to take out his appendix. Forgetting where you are going is incredible enough on its own. And not having any back-of-mind nag saying, "Wait a minute, we haven't heard anything on the air-traffic control frequency for a while" also is outside any known experience of the professional flight-crew world.
I say this not to rub it in for people who have lots of trouble ahead -- and who, to their credit, did get their passengers down safely. I mention it to underscore how much an outlier the apparent failure in this case is -- and to emphasize the trouble they're creating for themselves with the "conversation" and "laptop" alibis. If they fell asleep, that's embarrassing. If they were awake, it is far, far worse.