Drift down
Band a lot
It is not quite as simple as being above the terrain. If you have an engine failure or lose pressure at high level you must descend in accordance with a plan. The drift down must end above the terrain so where the terrain is higher than 10.00 you need to put some thought into it ahead of the problem, preferably before flight but in the cruise before reaching the higher terrain will do. Being above the highest terrain in the world sounds great but doesn't solve the problem