Airplanes can travel for thousands of kilometers across the world.

Rockets have landed men on the moon and elon musk wants to land men on mars

within the next couple years. The world has been made so small by us that it's easy to overlook some of 

the forgotten parts. For example airplanes are traveling through the skies pretty much

every where on earth at all times but if you were to open up a live global air traffic map

right now and pan over to asia you'll see nothing over this massive area of the continent

regardless of whenever you do this it. Always appears that all of the world's

airplanes are simply avoiding this huge area and going out of their way to fly around it like

it's some kind of forbidden zone to travel over or fly through and it's not

like this is the middle of the ocean. This is a huge area of land directly

over asia the world's most heavily populated continent. So why is this happening well there's a

lot of reasons but before we get into that you need to know about some aviation

history in the region.  The dead  question is over a geographic region

known as the tibetan plateau and it's one of the world's biggest wastelands.  After Antarctica and

Northern Greenland the Tibetan Plateau is the least hospitable place for humans

to live in the entire world and is the most sparsely populated. It's an area that's over five

times larger than France but only has a population of a little over 14 million people

across the seven countries that it spans over.

So few people live here because the plateau's average elevation is over 4 500 meters tall

making the tibetan plateau the highest geographic region in the world and earning it the nickname

the roof of the world.  The nickname is aptly deserved because the roof of theworld

has been one of the world's biggest obstacles to aviation for decades.

The first large-scale attempt to fly across the plateau was during the second world war when the

allies in what was then british india needed to airlift supplies into China to

assist them in the fight against the Japanese.  The route wasn't especially far

simply from eastern India into Kunmeng in China a distance of just a little over 840 kilometers.

But because they were flying over the remote mountains and high steps of the Tibetan plateau the

pilots faced extremely violent turbulence wind speeds up to 200 miles per hour.

Temperatures cold enough to freeze their fuel, implement weather events that were

difficult to predict and almost no emergency airports that they could divert to

in the event of an accident let alone the occasional intervention of Japanese fighters.

All of these hazards added up to an incredibly dangerous flight path that over the time span of 42

months saw 594 planes and 1 659 men who were lost in the mountains

never to be seen again.  The vast majority of these losses were a simple result

of the dangerous elements the pilots were flying through and not a result of enemy action and for

reference.  The loss in life for the allied air crews here was even higher than during

the entire battle of Britain against the Germans in some months as many as

50 percent of all allied planes that flew the route were crashing which would obviously

not exactly be an acceptable loss rate to a modern airliner today.

Luckily for the modern airliners the Tibetan plateau has been gradually opened up in the decades since 

thesecond world war. The first airport in Chinese, Tibet was built in 1956 and the modern airport in the 

Tibetan capital Lahasa was built a decade later in 1965.

Today there are two significant

International airports located on the

Tibetan plateau in Lahasa and Jining.  Both of these airports primarily handle domestic air

travel to and from the rest of China. But Lahasa has a single international flight to Kathmandu

while Zhening maintains flights to Taipei Tokyo and Kuala lumpur.

So it's true that there sometimes are planes flying over the Tibetan plateau

in modern times but almost every International flight between eastern Asia and the West

will go out of their way to avoid flying over it take this flight.  This flight or this flight just as a

handful of examples so now that we've gone through some history lessons.

Why do most airliners continue to avoid flying over Tibet on their longer flights today despite

the existence of modern International airports and you know being able to actually fly over

the mountains it ultimately comes down to four primary reasons that we're going to

go through the first of which is the stupidly huge risk during emergency situations.

Think about it like this the average elevation of the Tibetan plateau

is well over 14 000 feet and airliners usually cruise at over 30 000 feet normally not

a problem but under certain critical emergency situations like a

cabin depressurization or engine failure event airline protocol is to descend

down to 10 000 feet in a cabin depressurization scenario the plane will drop

oxygen mask for passengers to breathe.  But there's only a limited supply

generally only around 20 minutes.  This is intended to be enough time for the

passengers to last breathing on while the plane descends down to 10 000

feet where normal breathing conditions can be resumed.  Now obviously this isn't possible

anywhere over the vast Tibetan plateau that's over five times the size of France because the

average elevation is over fourteen thousand feet meaning that if a plane descended down

to ten thousand feet as protocol demands it would almost certainly crash into the

side of a mountain and everyone would die. If a cabin depressurization happens over Tibet

the only nearby major International airport safe enough

and close enough for most big airliners to divert to in an emergency are La hassa Jining Kathmandu 

Chengdu Urumki and Almady.   These airports are all hundreds or thousands

of kilometers away from each other and they mostly ring around the uninhabited plateau.

When a plane flies from Kathmandu to Lahasa for example Kathmandu and Lahasa are each the

alternate emergency airport in addition to being the destination in 2018.

A sichuan airlines flight was flying from Chongqing to Lahasa across the plateau at 30 000 ft when a

wind blew out and it suffered a depressurization event.   Fortunately the pilots weren't very far

across into the plateau.  So they were able to quickly turn around and divert to the airport at Chengdu 

for an emergency landing within 35 minutes of the depressurization happening the deeper an 

emergency like this happens into the plateau the more dangerous the emergency becomes

because of how far away you can get from any airports to divert to leading to longer times

up in the air without any oxygen.  This leads us into problem number two for why

airplanes don't fly over Tibet.  There's just nobody that really lives

there so there isn't really a very big demand long-haul international flights between

Europe and Asia will avoid flying over  Tibet because they don't want to risk

having an emergency situation while flying over it. But there aren't that many shorter

domestic flights either because there's just so few people there

the Tibet autonomous region in China has just a little over 3 million people who live across the

entire massive area meaning that despite Tibet taking up almost 13 of China's total land it only accounts

for 0.2 percent of china's total population.  The next two reasons why long-haul

flights avoid flying over Tibet are bad turbulence and the risk of jet fuel freezing.

When fast winds move across the plateau and the mountains the wind will often

take a wave-shaped pattern that looks like this and when airplanes fly through this wind

pattern the turbulence can get extremely bumpy which can further complicate any

emergency scenarios and finally there's the problem of jet fuel theoretically

jet fuel freezes when the temperature gets below minus 40 celsius and while extremely cold conditions 

like that rarely take place anywhere the jets fly.

The temperatures in the air above the already high and cold Tibetan plateau

can get to that point or worse.  This isn't really a problem for a short flight through

but for longer flights across the plateau that might last for six hours or more.

This can become a really significant problem.  Ultimately the big reason why airplanes almost

always avoid flying over the Tibetan plateau to get to their destinations

isn't because of any supernatural curse or something like that but a simple

reality that if they were to experience an emergency while flying across

it would perhaps be the most dangerous place anywhere over the inhabited

earth's continents.

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