midland 63,
Their first clue was the intermitent horn at 10,000 ft cabin altitude. Hypoxia didn't set in until several minutes later so if they knew their systems at all they should have realized the warning in flight is cabin altitude, not take off warning. It happened to me one day and I figured it out in a few seconds, as we are trained to do, so it was a non event. Blaming Boeing for using the same warning on the ground and in the air seems lame. They should have performed standard procedures to easily handle the situation.