I just read Mayday by Nelson Demille. I won't get into many details but the book talks about an airliner (similar to the Concorde) which operates at an altitude of ~60,000 ft (~18Km). Suddenly, due to a mistaken missile launch, there are holes on both sides of the plane. All the passengers become brain-damaged except 5 people who are trapped in lavatories at that time.
Now while this is fiction, could we go crazy due to lack of oxygen in case something goes wrong? How much oxygen would be needed to land safely and how much oxygen is usually kept on an airliner in case of emergencies.
A second and related question: in case of a fire or other incident, how quickly can a plane safely descend? I know and have experienced losing altitude the last 30 minutes or so of flight, probably lining up to the airport. In an emergency, how quickly can the pilot land? Is it 5-10 minutes or more? I am talking about descending from cruise altitude and come to a dead-stop.