So why did the missing 777 go to 40,000 feet??? Because the Pilot Oxygen Mask is rated to 40,000. The passenger masks only to 25,000 feet.
This is the system supplier to the Boeing 777...
So we go to 40K feet. Depressurize. Masks Drop. Everybody dies anyway. Now back down to 25,000 and off for 8 hours of quiet flying to.... somewhere.