Originally Posted by
James7
A sharp cabin crew could stay on O2 for hours with use of portable O2. Certainly outlast the pilots. Hiflo would keep them alive ( just) above 40k. Above 40k you need to pressure breathe. They would come round once aircraft descended to reasonable level.
You would need a massive quantity of portable O2. Consider a scuba cylinder will not last that long. Certainly it will last longer at height than at depth but not that long.
Our portable bottles, a lot lighter than a scuba cylinder, would last for perhaps 20 minutes at 20k.