Originally Posted by
DC-8
Other reason to fly above the optimum is to avoid meteorological adversities.
So, why would airlines want to fly higher?
GOL is a bad example. Look at the Pulkovo Tu-154, though.
Attempted flying over a thundercloud, near its ceiling. Whether it was also trying to turn around the weather or whether it hit a gust above the cloud, the - structurally intact - plane seems to have entered a flat spin. The plane never recovered and impacted ground.