The marathon thread on Helios seems to have sunk, but rather than add to its unwieldy 150+ pages, I thought it might be better to start a new thread.
Here's the
latest update on Helios in Flight, which is very much along the line that many here have supposed: failure of pressurization, and apparent crew confusion in recognizing this until it was too late. Nothing really new in this sense, but a recognition that there have been many similar cases, which fortunately had better outcomes.