Aircraft pilots and passengers need pressurized air and oxygen above 10,000 ft. Base camp for Everest is at 17,000. Altitude sickness becomes an issue above 5,000 and can be fatal the only treatment a return to lower altitudes. It is only one of the possible bodily reactions to thinning air. Health and conditioning are no predictors of whether these complications will hit. Sound like a tourist destination?
Aside from the body's reaction to lowering air pressure is the issue of thinning air and drop in available oxygen. The Sherpa's who make a living packing for climbers have lived their entire lives for generations at high altitude and their bodies have adapted.
If you've traveled to mountainous regions such as Banff and Jasper in Canada then you're aware of the body's need to acclimatize. Among other things the blood sees an increase in hemoglobin. Until that happens any exertion can leave you panting, suffering profound fatigue, head ache, and stomach upset. Cooking at elevation is another issue. Water boils at a lower temperature and baked goods require less leavening plus fires are harder to start and keep burning.
Back to Everest. Because it's there seems a fool-hardy reason to enter a death zone. Above Camp four on Everest the air is so thin it cannot support helicopter flight and the bodies of those who go there are dying. Remaining too long will kill you and getting trapped by weather is an ever-present danger and will result in your death. No rescue is possible at that elevation and the bodies of the dead litter the mountain as no one has the energy to carry them away.
Finally cold is an ever-present menace the temperature rarely rising above 0ยบ F and dropping to -30 with -60 wind chills. Plus with people from many nations gathering in polluted, pestilential third-world slum conditions diseases rapidly become epidemics. And yet people pay $100,000 or more to go there as tourists.
