While commercial planes are not specifically banned from flying over the Himalayas, there's an unsettling reason why they generally avoid doing it.

If you look at the flight paths of airplanes traveling around the world, you will notice several oddities. For example, they do not fly direct routes to their destination or avoid certain areas.

What remained unclear was the route Ekai Kawaguchi (1866-1945) took to enter Tibet, tucked deep in the mountains and closed to foreigners, at a time when no decent map was available. Now ...

This is the segment that winds through Tibet's remote Nyainqentanglha Mountains, an area so rugged and inhospitable it was simply abandoned decades ago and the entire area closed to travelers.