Original subtitles

(tense music)

NARRATOR: High above the Himalayas…

(cracks)

The windshield of Sichuan Airlines Flight 8633 cracks.

It’s on the inside. That’s not good.

NARRATOR: And then gives way completely. (explosion)

(shattering)

NANCE: It’s almost like having a bomb explode right beside you.

NARRATOR: The decompression forces the first officer halfway out of the plane.

LIU (yells): Xu!

NARRATOR: In freezing temperatures and rapidly running out of oxygen,

the captain needs to find a way to get his plane to safety.

Useful consciousness is probably about 40 seconds.

NARRATOR: The lives of everyone onboard now rest in the hands of one man.

I’m just so, so cold.

PILOT (over radio): Mayday! Mayday!

(alarm blaring) GPWS: Pull up! Pull up!

(indistinct radio chatter)

(engine roaring)

NARRATOR: High above central China,

Sichuan Airlines Flight 8633 reaches cruising altitude.

Level at 321.

Roger.

NARRATOR: 45-year-old Captain Liu Chuanjian

is a highly experienced former military pilot and a flight instructor.

We’re approaching an area of turbulence.

It shouldn’t be too rough.

NARRATOR: First Officer Xu Ruichen is 27-years-old

and has five years of flying experience, four of them with Sichuan Airlines.

The crew is flying an Airbus A319.

NANCE: The A319 is part of the Airbus A320 series.

It's a little bit shorter, a little bit lighter,

but with still two very powerful engines,

very well suited for taking a heavy load out of a high-altitude airport

where your weight and balance is extremely critical.

NARRATOR: There are 119 passengers on board.

Many catch up on lost sleep after an early morning departure.

It should be a smooth ride from here to Lhasa.

NARRATOR: The plane took off from Chongqing Airport.

It’s a two hour and 40-minute flight to Lhasa, tucked in the Himalayan Mountains.

They’re flying into Lhasa, which is one of the most demanding airports in the world.

It’s not a dangerous airport,

if you follow the rules and you watch the weather carefully.

NARRATOR: Captain Liang Peng is the second in command.

- I’ll be back well before landing. - See you then.

NARRATOR: He’s been a pilot for ten years.

Today, he’ll assist with the high-altitude landing in Lhasa,

which involves more challenging procedures.

PETCHENIK: This particular flight had three pilots;

a captain, a first officer, and a secondary captain,

because the aircraft was landing at a higher elevation airport

and those require specific procedures.

When you’re flying into a high-altitude airport,

you’re worried about performance issues

and you’re also concerned about the approach path through the mountains.

All three of the pilots involved here were very experienced with high altitude,

captain especially.

NARRATOR: There are five flight attendants on board.

Among them, Bi Nan, who’s been with Sichuan Airlines for 11 years.

Six minutes after reaching cruising altitude,

Flight 8633 crosses into the Tibetan Plateau,

the largest and highest plateau on Earth.

The altitudes are way above 20,000 feet,

not just for the peaks, but the plateau itself.

Chengdu Control, Sichuan 8633, reporting crossing Mikos Bravo 213.

Chengdu Control, roger. Sichuan 8633 at Mikos Bravo 213.

Not a cloud in the sky.

NARRATOR: 40 minutes into the flight…

(cracks)

(tense music)

XU: The windshield is cracked.

(beeps)

LIU: You got the checklist?

NARRATOR: Just as First Officer Xu finds the checklist, the situation deteriorates.

(cracks)

One of the procedures is to run your finger lightly over it,

and see if you can feel any bumps,

and try to figure out is this external or an internal crack.

It’s on the inside. That’s not good.

NARRATOR: A crack on the inner pane makes the windshield vulnerable to shattering.

Sir, it says here descend to a lower altitude.

CURTIS: The windshield of an aircraft actually has several layers of glass,

and this was the inner pane that was cracked.

The safe thing to do is divert to a safe landing zone.

It’s what we call a precautionary emergency, but it’s still very important.

I have control. I have the radios.

Chengdu, Chengdu, Sichuan 8633. We have a malfunction.

LIU: Requesting descent to a lower altitude.

Sichuan 8633, descend to flight level 280.

28,000 feet. I’m turning back. We have a cracked right windshield.

Sichuan 8633. Got it. Confirm… You have a broken windshield?

Affirmative.

Sichuan 8633, confirm will you divert to Chongqing?

Negative. We must divert to Chengdu. The window crack is severe.

Confirm, you will divert to Chengdu.

NARRATOR: As the pilots begin their descent…

Affirmative. We…

(explosion)

NARRATOR: …the cracked windscreen explodes,

sucking the first officer partially out of the window.

(beeping)

NANCE: The sound and fury of losing a windshield is something

like almost having a bomb explode right beside you

without it doing you any physical damage. It is soul shaking, to say the least.

(beeping)

All of the high pressure wants to go to the low pressure air.

So anything that isn't attached is going to want to escape through that hole,

including a human being.

(beeping)

(screaming)

(gusting wind)

Sichuan 8633, roger. Descend and maintain flight level 280.

NARRATOR: As the aircraft dives toward the mountains,

the first officer hangs on at 32,000 feet above the Earth.

When the first officer was pulled forward,

he impacted the sidestick, and that pushed the aircraft down and to the right.

This flight is over high terrain,

so it has a much higher probability of impacting terrain more quickly.

NARRATOR: On the ground, the controller notices a sudden shift in altitude.

ATC: Sichuan 8633?

NARRATOR: With no time to review all the warnings, the captain returns to basics.

He begins to fly the plane manually.

There were a number of different warnings happening at the exact same time.

But the most important thing is to fly the airplane,

focus on maintaining a safe altitude.

(beeping)

NARRATOR: Captain Liu regains some control and levels the plane.

But he’s facing oxygen deprivation from the rapid decompression.

PETCHENIK: In the case of an explosive decompression at cruise altitude,

hypoxia will set in fairly quickly.

NARRATOR: As it’s stowed in a compartment to the left and behind the pilot’s seat,

Captain Liu can’t reach his mask with his right hand.

His left hand must remain on the sidestick.

(dramatic music)

At about 31,000 feet, the time of useful consciousness

is probably about 40 seconds for a healthy individual.

This is something that you can't play around with, because it is lethal.

NARRATOR: The captain can’t get his first officer back in.

He’s on his own.

The former fighter pilot knows if he can’t make a rapid descent,

there’s no hope of saving his passengers,

and his helpless first officer.

(dramatic music)

Immediately after Flight 8633’s cockpit windshield shatters,

Captain Liu tries to return to Chengdu Airport.

PETCHENIK: This is an incredibly stressful situation.

The first officer has been partially sucked out of the aircraft.

The captain needs to get down to breathe.

But the mountains are higher than that breathable oxygen.

NARRATOR: To get out of the mountains quickly,

the captain puts the Airbus into a sharp, descending left turn.

In a emergency situation, the pilots going to maneuver the aircraft outside

what would normally be an acceptable envelope.

(gusting wind)

(yells) Xu! Can you get back on your own? I can’t let go of the control stick!

After the first officer is sucked out of the windscreen,

he’s trying to get back into the aircraft.

NARRATOR: 61 seconds after the windshield explodes,

the pressure between the internal and external air equalizes.

Once the pressure equalizes between the flight deck

and the exterior of the aircraft,

the first officer is able to bring himself back into the aircraft.

Xu! Xu! Are you okay?

Get your harness!

NARRATOR: With the pressure equalized,

the airstream reverses, and an ice-cold wind comes rushing in.

Your mask too!

NARRATOR: High winds hamper the first officer’s efforts.

If you’re flying at 30,000 feet, it could be 40 degrees below zero.

So you have not only the extreme cold,

you also have the extreme pressure of the wind coming in at you.

(gusting wind)

NARRATOR: With the first officer safely back inside,

the captain accelerates his descent to the airport, 71 miles away.

Can you reach the transponder?

NARRATOR: Liu wants to notify air traffic control of their emergency.

(tense music)

(beeping)

When an aircraft squawks 7700 on the transponder,

it identifies the air traffic controllers in the area

something is wrong and that aircraft needs priority.

Sichuan 8633, what is the nature of your emergency?

Sichuan 8633?

Tibet 9832, Chengdu.

NARRATOR: The controller contacts other pilots for help.

PILOT: Tibet 9832. Go ahead.

Could you call Sichuan 8633 on the frequency? They’ve got an emergency.

Let’s see if you can get through.

PILOT: All right.

Sichuan 8633, this is Tibet 9832. Chengdu control is calling you.

NARRATOR: In the cabin, Captain Liang retrieves his electronic flight bag.

HAUETER: The electronic flight bag on the aircraft provided

the crew with the escape routes they could fly

to get to lower altitudes in the mountains.

(gusting wind)

- Give me a hand with the navigation! - LIANG (yells): Copy.

Your mask.

I’m good for now. I can’t let go of the controls.

LIANG: Altitude is 23,700.

NARRATOR: As the plane nears the lowest altitude

it can fly over mountainous terrain, the captain levels off.

- LIU: Speed? - LIANG: 297 knots.

The cabin has oxygen masks. Bi Nan is in charge.

- Xu? Can you hear me? Are you hurt? - I’ll perform the FO duties.

NARRATOR: With First Officer Xu too injured to assist,

Relief Captain Liang takes over his duties.

- Got the escape chart? - LIANG: On it.

NARRATOR: Captain Liang checks the charts

for the safest exit route over the mountains.

LIANG: Chengdu is 63 miles away. Continue descent at 500 feet per minute,

then level at 22,000 until we clear the mountains.

(stutters) Copy.

LIANG: I’ll call the altitudes.

The second in command can see that the captain is handling this.

But there are things that have to be done,

and one of them is making sure that they don't go too low.

NARRATOR: The Airbus reaches 23,400 feet and is nearly out of the mountains.

LIANG: You can do it.

I’m just so, so cold.

NARRATOR: Captain Liu is fearless. But at this altitude, he risks hypothermia,

and the airport is still 60 miles away.

(dramatic music)

NARRATOR: 12 minutes after a rapid decompression,

Flight 8633 clears the towering Tibetan Plateau.

LIANG: 34 miles to the airport! Getting there, Captain.

NARRATOR: Captain Liu turns the plane towards the airport.

LIANG: Altitude is 20,900.

(stutters) Copy.

CURTIS: They were able to get beyond the mountains. Then other concerns.

Do we communicate with air traffic control? Do we set up for the landing?

LIANG: Chengdu, Sichuan 8633. Mayday. Mayday. Mayday.

Message received. Mayday declared.

Sichuan 8633 cleared to descend to flight level 190.

Siberia 581, climb to flight level 250, off-set three miles.

NARRATOR: The controller clears the airspace around the damaged airplane.

West China 6271, maintain flight level 160 and off-set three miles.

(tense music) (rattling)

NARRATOR: In the cabin, Bi Nan tries to contact the crew.

PETCHENIK: The flight attendants are doing their best

to ensure that the cabin is calm, everyone has their supplemental oxygen.

But one of the complicating events here

is they never get into communication with the flight deck,

to understand the full scope of the situation.

NARRATOR: Flight 8633 is now 28 miles from Chengdu.

Approaching 19,000 feet.

NARRATOR: The captain can breathe a little better now.

Roger. Roger.

Hang in there Xu.

Sichuan 8633.

Cabin depressurization. Flying direct to Chengdu, then descending to… 10,500 feet.

Flying direct to Chengdu, then descending to 10,500 feet.

PETCHENIK: The crew's transmitting in the blind

because they’re trying to tell air traffic control their intentions,

but they can't hear anything that air traffic control is saying

because of all of the noise coming in from that missing window.

Look over the warnings.

NARRATOR: As the flight makes its way towards the airport,

the pilots assess the state of their aircraft.

The captain knows the windscreen is gone. He knows that the control panel is gone,

but he doesn't know exactly what else has been damaged on the aircraft.

LIANG: Auto-brakes are gone. Anti-skids, spoilers, APU.

They’ve all got warnings.

NARRATOR: With so many instruments potentially inoperative,

the landing must be performed manually.

This was a highly automated aircraft.

When you have damage like in this incident,

that automation is taken offline.

And they have to figure out how to land the airplane.

LIU: Okay. Okay.

LIANG: Do you want to try the autopilot?

Too risky.

NARRATOR: Re-engaging disabled instruments

is a gamble Captain Liu isn’t willing to take.

He could lose what little control he has over the plane.

NANCE: That is great airmanship to just take what he has and work with it.

Because in an emergency, you don't know exactly what you’re gonna get.

Sichuan 8633, orbit to the right and descend 8,800 feet

on QNH 1004 at present position. You’re cleared to land on runway zero two.

NARRATOR: Flight 8633 makes a 360 degree turn to lose altitude

while preparing for landing.

- LIANG: 11,200 feet. - LIU: Copy.

We’re still above our maximum landing weight.

LIANG: We’re heavy by half a ton.

NARRATOR: The pilots must factor in the extra weight of their unused fuel

as they prepare to configure the plane for landing.

An overweight landing on an Airbus A319 where you can't dump fuel

means that you’ve got to be much more careful

in terms of actually touching down.

You may have more difficulty stopping the airplane.

Flaps one!

NARRATOR: They don’t know yet if deploying the flaps will slow the plane.

LIANG: Flaps one set.

Yes!

- The flaps are working so far! - Good. Speed?

LIANG: 212 knots.

LIU: Reducing to 203.

NARRATOR: The pilots slow the engines further.

(tense music)

Bi Nan can sense that the plane is approaching the airport.

Attention everyone. Please remove your masks.

NARRATOR: She prepares the cabin for an emergency landing.

Tuck your head in your lap and brace for impact.

Landing gear!

LIANG: Roger. Landing gear.

NARRATOR: So far, the plane is slowing.

The pilots still don’t know if the landing gear will engage.

Yes! Landing gear is down.

Cleared to land on runway zero two, right. Wind 250 at two meters per second,

R-V-R greater than 6,500 feet.

We need the whole runway.

Sichuan 8633. Runway zero two right. We need the entire runway.

PETCHENIK: The captain selected that runway

to account for the fact that the aircraft is heavier,

and therefore is requiring more stopping distance.

NARRATOR: Ten miles from the airport, the aircraft is lined up with the runway.

160 knots.

After everything that’s happened, can they keep it on the runway?

(tense music)

50 feet! 40 feet!

NARRATOR: The 63-ton plane prepares to touch down.

(tires screech)

Engaging thrust reversers.

NARRATOR: The thrust reversers, which help the plane slow down, aren’t functioning.

The risk is that you’re gonna run off the end of the runway

- if you don’t have your thrust reversers. - Brakes! Brakes!

NARRATOR: Captain Liu gives the foot brakes everything he’s got.

They’re his last hope of stopping the plane from overshooting the runway.

(sighs)

We made it.

(applause)

(gasping)

Sichuan 8633, we have injuries on board and cannot taxi to the gate.

NARRATOR: Against tremendous odds,

everyone on board Sichuan 8633 is safely back on the ground

thanks to the pilots’ exceptional skills.

CURTIS: Once everyone was able to exit the aircraft safely,

the real work of the investigation began.

What evidence can they find that will help them answer the question:

Why did this happen?

(cool music)

NARRATOR: Investigators from the Civil Aviation Administration of China,

or CAAC, look into Sichuan 8633’s near catastrophe.

- Good to see you again. - You as well.

- Do you wanna look at the cockpit? - That’d be good.

NARRATOR: A French investigator from the

Bureau of Air Accident Investigation and Analysis, or BEA, also joins the team.

Okay. I’ll speak with Captain Liu while one of our team takes you to the plane.

Great. Thanks.

HAUETER: The aircraft is made in France.

The BEA, as the investigative agency for that country,

would respond to an accident worldwide.

Thank you for coming in. Oh, please, have a seat.

NARRATOR: Did something strike the windshield of Flight 8633,

causing it to rupture?

LIU: It was a clear day. We were cruising along at 32,100 feet.

About ten minutes in, we heard a loud noise and saw a big mesh crack.

And then?

A few seconds later, another loud noise and the crack radiated further.

I touched the glass. And I could tell it was on the inner pane, and it was bad.

NARRATOR: A cockpit windshield is made up of three layers of glass;

two thick inner panes and one thin outer pane.

HAUETER: The windshield's actually a structural part of the airplane.

They’re quite thick. They’re very strong.

Obviously they’re made to withstand your bird strikes and other objects like that.

- LIU: I called ATC to clear descent. - You told them the windshield was cracked?

Yes, but before we finished talking, the window exploded.

A decompression happened and we lost a bunch of instruments.

Did you see anything hit the windshield?

No. There was no mark, no smear, just a big mesh-like crack.

Okay. Thank you. If I have more questions, I’ll reach out.

NARRATOR: Investigators rule out an external strike

as the cause of the windshield’s explosion.

Thanks for your time.

HAUETER: There’s no evidence of lightning strike or birds or anything else.

So there was nothing to show that that piece of the windshield

was damaged prior to the event.

- Any signs of how the crack started? - Not really.

Almost everything was sucked out of the windshield.

- (hums) - Except this.

The terminal block.

NARRATOR: Located at the bottom of the windshield,

the terminal block holds six electrical wires

that control the temperature to prevent freezing or fogging.

The team is dismantling it from the frame so we can take a closer look.

Okay.

The investigators focused on the terminal block

because it was the only part of the windscreen assembly that they had left.

INVESTIGATOR: Let’s download the data now.

NARRATOR: While investigators wait for the terminal block

to be removed from the plane,

they turn to one of the flight’s communication systems for leads.

A digital communications system called ACARS,

or Aircraft Communication Addressing and Reporting System,

sends electronic messages between the aircraft

and ground stations during a flight.

ACARS messages coming from the aircraft

can lead the investigators to certain faults that occurred

as well as what the aircraft was doing.

It’s all here. Let’s locate the first crack.

Here it is. 7:07 am.

See that?

Anti-ice right windshield. Huh. Interesting.

NARRATOR: Investigators discover that after the windshield first cracked,

there was a warning message. (beeps)

The anti-ice message gives you an indication

that there is something wrong with the heating element in the windscreen,

but it doesn't exactly tell you why.

CURTIS: The windshield cracking and the warning happened almost simultaneously.

The investigators had to think there has to be a connection.

Let’s check recent flights.

NARRATOR: Has an anti-ice windshield warning appeared on other flights?

Investigators search the fleet’s history.

Check this out.

2009, the warning popped up on a Sichuan Airlines flight after takeoff.

NARRATOR: In 2009, the warning also appeared

as Jiangsu Airlines pilots detected smoke near the bottom of their windshield.

In 2010, the warning lit up on a China Hubei flight

when pilots noticed a burning smell near the windscreen.

- Did they determine a cause? - Overheating. In all three cases.

Investigators saw that in related incidents

where this kind of warning came up, there were certain effects,

burning smells, anything that indicated there was an overheating happening.

What about the windshields? Did any of them crack or rupture?

INVESTIGATOR: No. It doesn’t look like it.

Sichuan 8633 never reported smoke.

Nor the smell of burning.

CURTIS: The investigators knew

there was a problem with the right windshield heating system.

So what was different about this incident?

Let’s see what the terminal block can tell us.

NARRATOR: Investigators turn to physical evidence

from Sichuan Airlines 8633’s cockpit for clues as to why the windshield shattered.

Check out these wires.

CURTIS: The windshield heating system is electrically driven

and there are several wires through the terminal block

that help drive this system.

One of those wires looked a lot more damaged than the others.

Huh. It looks like the wire insulation is charred and the copper wire is melted.

NARRATOR: The team finds evidence of overheating.

They noticed that one of the wires was very dark,

which is a sign of carbonization.

HAUETER: They could see evidence of burning heat around the end of it.

INVESTIGATOR 2: Look at the corrosion inside the terminal block.

NARRATOR: Investigators also find evidence of moisture build up.

Water must have seeped in past the window seals.

They discover signs of moisture and humidity

and even unusual color you should not see inside a terminal block.

NARRATOR: Moisture inside the terminal block

corroded and damaged the copper wires.

When a current ran through them, arcing occurred,

which created extremely high temperatures.

(cracks)

HAUETER: You’re reading temperatures in excess of 400 degrees Celsius.

It's extremely hot.

CURTIS: The investigators had to answer:

Was this enough to make the windshield crack?

NARRATOR: Investigators dig into the history of the aircraft,

looking for a connection between cracked windshields and overheating.

Got one. An A340, December 1997.

I found four more.

2001, 2004, 2007 and 2011.

Here’s another one from 2009.

NARRATOR: They discover six incidents of double pane cracks in cockpit windshields.

Every single incident resulted from overheating.

The heat built up inside the windshield and couldn’t dissipate.

Which is why the windows cracked.

NARRATOR: The team concludes that an overheated electrical wire

inside the windshield cracked the inner pane of glass on the first officer’s side.

CURTIS: The aircraft windshield panes are very closely spaced together,

and when one side is overheated it spreads those panes apart.

It causes stresses on those panes.

NARRATOR: But a windshield cracking

is vastly different from completely separating from the aircraft.

How did Sichuan 8633’s windshield explode?

HAUETER: We know the first pane cracked.

The middle pane should have maintained loads and kept this intact.

But it failed very quickly. That was a mystery.

NARRATOR: To determine why Sichuan 8633’s windshield ruptured after cracking,

the team undertakes a Windshield Failure Scenario test.

CURTIS: The mechanism of what happened in-flight to that windshield is unknown,

because they didn't recover the windshield.

What they could do and what they did do

was to do a laboratory test to see if you can have a catastrophic failure.

NARRATOR: They install a cockpit windshield with a cracked inner pane

onto a test bench, replicating the first crack.

(grunts) Okay, the window’s ready.

The camera is now recording.

(air hissing)

Now pressurizing.

NARRATOR: The investigators set the test chamber

to the same differential pressure of Flight 8633.

Let’s get the shot pin ready.

NARRATOR: A small hole is drilled in the outer pane,

through which a shot pin can pass and strike the inner pane

in order to simulate the second pane cracking.

All set.

(tense music)

(explosion) (shatter)

(sighs)

NARRATOR: The test works. The windshield is blown clear of the frame.

Well, there you have it.

INVESTIGATOR: The pressure was just too much.

NARRATOR: At 32,000 feet, the difference in pressure

between the outside atmosphere and inside the cockpit was approximately two tons.

Investigators conclude that the cracked windshield

could not withstand that pressure.

What we saw from testing is once you break the inner pane and the middle pane,

the outer pane cannot withstand the pressure.

It’s going to flex the window out and it’s going to depart the aircraft.

(engine roars) (explosion)

- Here you go. - Thank you.

NARRATOR: Investigators now know how the windshield was blown from Flight 8633.

But they still don’t understand

why the moisture build-up inside the window was undetected.

Moisture’s insidious. It’s gonna find ways to get in.

So now the question is when they were inspected, how they were inspected?

The left and right window seals were replaced a year ago

because of wind erosion.

NARRATOR: Investigators examine the inspection history

of Flight 8633’s windshields.

That’s right. Flip the page.

The last inspection was 32 days before the incident

and there were no signs of water buildup on the terminal block. How come?

Maintenance would have had to remove the entire windshield to access it.

They'll look around the edge to see are the seals intact, are the seals degraded.

You look at components to see if there’s any evidence of water intrusion.

But you don't pull the window out of the frame.

So without fully disassembling the aircraft,

you can't ensure that you don't have water vapor built up.

NARRATOR: But that’s not all they discover.

There were no sensors to detect moisture.

HAUETER: You have sensors for controlling the temperature of the window,

but there’s nothing in there to tell you that corrosion’s present.

NARRATOR: Even though investigators understand

what caused the incident aboard Flight 8633…

You know what I don’t get?

NARRATOR: There’s one piece of the puzzle missing.

Why did so many systems in the cockpit fail after the windshield exploded?

(engine roars) (explosion)

(gusting wind)

(beeping)

With the loss of the windscreen,

also came a whole list of things that went off. It was puzzling.

They lost the auto-brakes, six of the ten spoilers, the thrust reversers.

NARRATOR: Investigators review all the systems the pilots of Flight 8633 lost

after the explosive decompression.

(hums)

It looks like they were disabled, not damaged.

NARRATOR: The team discovers that all the disabled systems on Flight 8633

are connected to 17 circuit breakers on a panel behind the first officer’s seat.

Check out all these popped breakers.

INVESTIGATOR 2: Something must have hit the breaker panel

during the decompression.

INVESTIGATOR: There’s damage here.

This part of the door lines up with the damage.

NARRATOR: The damage to the panel is at the same height

as the dented cockpit door.

(explosion) When the windshield ruptured,

the explosive decompression flung open the cockpit door,

which smashed the circuit panel and popped multiple breakers.

It’s almost impossible to think that anybody would immediately recognize

that that was a mechanical response to the door blowing open

and hitting the side panel.

NARRATOR: Investigators finally have all the pieces of the puzzle.

Moisture seeped into the window seals of the Airbus A319…

You couldn’t ask for a better view.

NARRATOR: Creating a humid environment where electrical wires overheated…

(cracks)

…to the point of cracking the glass panes on the cockpit windshield.

Sichuan 8633, confirm will you divert to Chongqing?

Negative. We must divert to Chengdu. The window crack is severe.

NARRATOR: The tremendous pressure differential

compounded the existing thermal stress on the cracked panes,

leading to the rupture and explosive decompression.

With his first officer sucked out of the window,

Captain Liu’s quick thinking, flying skills,

and tremendous courage in the face of oxygen deprivation

allowed him to fly the plane out of danger.

The captain didn't suffer from hypoxia.

Investigators looked at the surrounding factors,

and kind of came to the conclusion that he was operating

purely on adrenaline, basically, and was able to operate the aircraft safely

down to Chengdu.

LIANG: You can do it.

NARRATOR: The crew endured glacial temperatures

and battled the odds to safely land the damaged plane

and save the lives of all 128 people on board.

Any accident and incident investigation is also learning opportunity.

There were changes that were made by the manufacturer

to tighten up the quality control to make it less likely

that you would have situations that might allow moisture to get past the seals.

NARRATOR: The crew’s handling of the incident

earned them accolades around the world.

There have been accidents in the past where

whatever happened at altitude was survivable,

but the crew got so rattled and was so non-communicative,

they end up crashing the airplane on the other end.

This crew did a really excellent job.