Jon, we certainly should be carrying O2 as backup. The biggest problem in these events revolves around one of the following: 1) the loss of cabin pressure is gradual, and unrecognized for some time, 2) there is no O2 in the system (leaks, prior use, etc.—we should all have the gauge level check on our preflight list); the system doesn’t work (loose hoses, etc.), 3) relating to the first item, if the pressurization loss goes on for a while before recognized, the pilot can lose common sense before consciousness—not remembering which way to turn the valve on the tank under the seat, forgetting how to program the auto-pilot for lower altitude, be more concerned with high fuel consumption down low (turbine guys) leading to poor prioritization of needs (save gas vs. save life) and poor cockpit resource management. As pointed out in other posts, we lose tolerance to hypoxia as we age, as well…

I have a rule that if flying above FL 200, I always have the mask out and dangling around my neck; and yes, I always check the gauge under the seat when I climb in…

Douglas W. Johnson, MD PA

Ret. USAF Flight Surgeon, in another life…