The top of Mount Everest is some 29,000 feet ASL, which is
above the cruising altitude of some smaller passenger jets.
AFAIK There are no helicopters designed to work at or around 29,000 (FL 290). In fact, in the Krakauer book Into Thin Air, there is talk about some brave helicopter pilot flying up toward the base camp (21,000 ft or something like that) to rescue the climbers. The pilot had to ferry the injured climbers one at a time, because he couldn’t generate enough lift to carry more than that.
My impression is that most people die on the return trip. The weather may no longer be good, you’re tired, you may be running out of oxygen, and falls are probably more likely when going downhill.
From Krakauer’s and Boukreev’s books, it seemed like many climbers have had it by the time they hit the summit and care more about getting somewhere warm and dry then enjoying the location and achievement.
The postscript to the IMAX film in question expressly states that much of the mountain footage was in fact filmed in the United States.
I’ve seen it several times, but I’m not sure of the wording of the disclaimer. I’ve walked away with the distinct impression that much of the filming was recreated and filmed elsewhere. The shots from the summit are, with the exception of one truly grandiose panning shot, largely still photos and 16mm motion picture. IMAX rolls are only minutes long in the cameras designed for portable use. I wouldn’t be suprised at all if the one summit panorama is all that was considered usable footage.