In reply to planetmarshall:
> This seems a bit old hat, surely? Krzysztof Wielicki did a 1 day ascent of Broad Peak back in 1984. Over 30 years ago.
Wielicki was amazing, but it's important to compare apples with apples.
The closest to what Jornet is trying was done by Loretan and Troillet in Aug 1986 (one of the very few similar 'summer' climbs) when they went up the Hornbein/Super Couloir in 38hrs and slid down in 3hrs. But they started from a bivi at the bottom of the face, around 6000m. Jornet is planning to run from the very start, at Rongbuk, around 15-20km all the way up the glacier to the bottom of the face and keep going up. Nothing like this has been done on Everest.
Wielicki's BP climb was done from a closer camp, up a route that had had traffic on it, to a summit 800m lower than Everest's summit. It's the last few hundred metres, above 8500 or so, that really slow down climbers trying to go light and without bottled O2. There have been several climbers get high on the north face of Everest, over 8300m, going light with no O2, but they've nearly all turned back, just going too slow, too cold, all too hard. In 1987 Pierre Beghin and Fernando Garrido turned back at 8700m!
Most of the very fast one day 8000er climbs have been done on booted tracks, sometimes with fixed ropes (such as Benoit Chamoux's 23hr K2 climb) and other support. G2, Shishapangma, Lhotse, Everest north ridge etc have all been climbed like this.