All language subtitles for Mayday.S06E01.Ripped.Apart.1080p.AMZN.WEB-DL.DD+2.0.H.264-playWEB_track3_[eng]

Every passenger jet
is a travelling
life-support system,

carrying inside it
the highly pressurized oxygen
that keeps us alive.

If it ever escapes,
a simple flight
becomes a living nightmare.

United 811.

There was nothing in front
of us, or to the side of us.

The whole side
of the plane was gone.

Aloha 243...

Everything was going,
was being sucked out
of the plane.

British Airways 5390...

I'll never forget.
His face was hitting
the side screen,

but he didn't blink.

Mayday!
Mayday! Mayday!

Declaring an emergency!

Sometimes it takes
a terrible accident
to expose hidden dangers,

and change the way
airplanes are built.

Unfortunately, we wait
until we have enough bodies.

Too many of the changes
have been, in effect,
written in blood.

Mayday, mayday!

This is the assembly plant
for the Airbus A320.

After the Boeing 737,
it's the most popular
jet plane ever built.

Almost 2000 of them are flying
for airlines around the globe.

It's safe and dependable,
the airline equivalent
of a minivan.

The aluminum skin on the top
of an A320 is less
than two millimeters thick,

about as thick as a coin.

But this slender piece of metal
helps keep passengers alive...

because the skies aren't nearly
as friendly as they seem.

Most people
take aviation absolutely
for granted.

The difference between being
on a commercial airliner
at 35,000 feet

and being in a space capsule
in orbit is really not all that
different.

They're both life support
systems.

The reality is,
it's a hostile environment.

The reality is, it's 50 degrees
below zero outside.

The reality is that jet stream
or air stream out there,

it would kill you
almost immediately.

It's not natural
for people to travel
through this killer atmosphere.

But, every day,
millions of us fly easily

some 3,000 meters higher than
the top of Mount Everest.

All our life support
that's natural for us

is down here, at the bottom
of this sea of air.

And if we swim up too high,
however we get there,

if we're not protected,
we can't live.

But taking oxygen with us up
to 11,000 meters

is potentially dangerous.

The air inside an airplane
is pressurized, so passengers
can breathe easily.

As planes climb,
the pressure outside decreases.

The tightly packed air
in the cabin begins

exerting tremendous pressure
on the fuselage.

On an average jetliner,
it means that every square
meter of the fuselage

must support more than
5,000 kilograms of force.

And, on almost every flight,
the fuselage wins the battle.

But only because
airplane designers have learned
tragic lessons.

We have concentrated,
in the past,
on changing things.

But, unfortunately, we wait
until we have enough bodies.

In the 1950s,
a series of shocking accidents

triggered changes
that are still seen today.

The Comet has blazed new trails,
achieving new speeds,

setting a new standard.

The passenger jet era began
in the 1950s,

with the introduction
of the De Havilland Comet.

For the first time,
jet engines were being used

to push commercial planes
higher than ever before.

What Great Britain had at stake
with the comet was enormous.

They wanted to really declare
their place in civil aviation

by having the first successful
jet transport aircraft.

But less than two years
after its maiden flight,

the glittering jewel
of British aviation
disintegrated in mid-air.

It would have been
horrible.

It would have been
a horrible situation,

but mercifully,
it would have been quick.

What they had found
with the bodies
that they had recovered,

was the massive decompression,

of course, caused the air
inside your lungs
to burst your lungs.

At the same time, the out rush
of air would tear you
from your seat,

and that many of these people
actually smashed

their heads
against the structure.

Three months later,
another Comet ripped apart
in flight.

Officials feared
that every single Comet
could be a flying time bomb.

The entire fleet is grounded.

The design of The Comet
was actually
a very sound design.

There was only one thing
that they didn't do,

and it's because nobody knew.

Unknown to engineers,

there was a deadly flaw
in The Comet's basic design.

To find the jet's
fatal weakness,

investigators built
a massive water tank.

They immersed
a stripped-down Comet.

The pressure in the tank
was increased and decreased,

simulating the strains
of flights

The experiment ran
24 hours a day,

seven days a week.

After the equivalent
of some 3,000 flights,

The Comet's Achilles' heel
revealed itself.

Its square windows.

You have
a rapid change
of direction in the shape,

essentially a corner,

you have
a high stress concentration.

It gave rise
to a fatigue crack,

which then travelled rapidly
through

the rest of the structure,
causing a massive decompression.

The most advanced passenger jet
in the world had succumbed

to metal fatigue.

The fuselage simply could not
handle the force
of the air inside pressing out.

The airplane, with all that
force behind it,
suddenly unzipped itself.

Every plane that's built today
is safer

because of the disaster
that struck The Comet.

Like other passenger planes,
the windows
on the A-320 are rounded,

so that pressure doesn't
build up around the corners.

Perhaps even more importantly,
extra rivets reinforce the skin
of today's planes

to contain cracks
that might start anywhere
on the fuselage.

It's designed to go
to that first row of rivets
and absolutely be stopped.

It's a healthy structure.

It can never unzip itself.

But 34 years
after The Comet crash,

aircraft manufacturers
were faced
with another tragic disaster.

The extra rivets that were
supposed to save lives

failed to withstand
the relentless power
of air pressure on metal.

One of the fellows
that I knew at the FAA,

he said, "You know,
the day after this accident,

I had to throw away most of what
I knew about metallurgy
and start over."

At this Airbus factory
in Toulouse, France,

A320s roll out
at about the rate
of one every working day.

Titanium rivets, lightweight
and extremely tough,

hold the fuselage together.

Three thousand are used
to join the separate sections.

Another 3,000 can be found
on each wing.

Without them,
the fuselage couldn't contain
the pressurized air

that's forced
inside during flight.

But even
these rivets aren't foolproof.

April the 28th, 1988.

Aloha Airlines Flight 243
is traveling
from Hilo Airport

on the Big Island to Honolulu.

With this island hop,
Aloha 243 is making
its ninth flight of the day,

a normal schedule
for the planes of Aloha.

Protected within the jet,
passengers give little thought
to the fact

that the cabin is filled
with pressurized oxygen.

It's constantly pushing
against the fuselage,

trying to escape into
the surrounding atmosphere.

In the cabin,
the pressure is kept
at a constant level,

so passengers feel
like they've never
left the ground.

But as a plane rises
to its cruising altitude,

the air pressure
outside the cabin
is dangerously low.

Well, what we do is,
extract air from the engines

and use that
to pressurize the airplane.

And what we can do then
is control the pressure inside
by a series of valves.

The air moving
through the cabin
creates constant pressure

on the jet's fuselage,
keeping it inflated
like a balloon.

Every modern jet is built
to withstand this pressure.

There's
an internal structure
to a modern all-metal airplane.

The skin, without the structure,
would collapse easily.
It would buckle easily.

It would be sort of like a,
you know, a paper bag

without any structure inside
to hold it.

If you remove the skin
of a passenger jet,

you'll find hoop-shaped
bulkheads and formers

supporting the width
of the aircraft.

Stringers run the length
of the plane.

They all help support
the fuselage.

And the cabin needs
all the help it can get,

because, as the plane
gains altitude,

that pressurized oxygen
inside the plane

is pushing against
every square centimeter.

On this day in April, 1988,

passengers are about to learn
what happens
when that air suddenly escapes.

I saw a brilliant flash
of light. And, boom.

Everything was going,
was being sucked out
of the plane.

Aloha Airlines 243
has just suffered what

experts call
an "explosive decompression."

he air inside the plane
that makes jet flight possible

escapes in a sudden,
horrifying moment,

Thirty-five square meters
of the fuselage are gone.

Just imagine
the scene up there. The top
of the airplane broken off.

You now have 300 mile
an hour winds
blowing in that cabin.

That's three times
hurricane-force winds.

Those people were dressed
for Hawaii in the springtime,

not minus fifty-degree
temperatures.

Any period of time
at 24,000 feet,
those people will die.

What was that?
We have to get down!

Captain Bob Schornstheimer begins
an emergency descent,

dropping 20 meters a second.

The stress on the damaged craft
threatens to tear it apart.

The woman
that was sitting next to me,
and her husband,

he was on the other side
in the next row.

And she was next to me,
and they were reaching
their hands out,

and they were trying
to touch fingers
to say goodbye.

Against incredible odds,
the flight crew land

their bruised
and battered airplane.

Even with this explosive
decompression,

there's only one death
on Aloha Flight 243,

a flight attendant
who was pulled out
of the plane.

Jim Wildey investigates
the crash for the National
Transportation Safety Board.

In his laboratory,
Wildey makes
a disturbing discovery.

Running through some
of the pieces
of the plane's fuselage,

he finds a series
of hairline cracks.

They're right beside the holes
created by rivets

and barely visible
to the naked eye.

But they're classic signs
of metal fatigue.

Metal fatigue is something
that sounds exotic,

but it really is easy
to understand.

Any piece of metal has
a certain breaking point.

All of us have tried
to open a tin can

and not quite gotten the opener
all the way around.

We work it back and forth
until that last portion breaks.

You just demonstrated
metal fatigue.

A plane isn't
a rock solid tube.

To maintain the pressure
passengers need to enjoy
a flight,

it's designed
to be much more flexible.

The fuselage of the airplane
is actually breathing.

It expands and contracts
depending on altitude.

When it's on the ground,
it's in a contracted status.

When it's at altitude,
24,000 feet,
the fuselage expands.

If you could stand
at the back

of a 250-foot-long jetliner
and just sight
along that fuselage,

you'd see it begin
to puff up a little bit.

And as a plane lands,
the pressure differential

between the inside
and the outside
of the plane disappears.

The fuselage returns to normal.

So the airplane
is constantly cycling.

That's pressurization.
That will weaken the structure
over a long period of time.

Records show
that the Aloha jet
was 19 years old.

Boeing 737s are designed
for a 20-year service life,

and a recommended
75,000 flights.

But as investigators take
a closer look,

they discover that the Aloha jet
had logged an astonishing
89,000 separate flights.

The short hops
between the Hawaiian Islands

meant that the planes
in the Aloha Fleet

went through
more pressurization cycles
than any other aircraft.

You saw something
as you got on this airplane.

- What did you see?
- Investigator
Jim Wildey gets a lead

when he interviews
one of the Aloha passengers.

She says she saw a small crack
in the fuselage just
to the right of the door.

The witness saw cracking
in this area,

and we found fatigue cracking
back in here.

So this is the line
where the fatigue cracking
joined up.

One piece came down this way
and folded off,

and the other piece went
across the top and came off
to the right side.

But something doesn't
make sense.

The Aloha jet lost
35 square meters
of its fuselage.

In the years
after The Comet disaster,

Boeing and other companies
had designed a safety feature

that should have kept
any tearing
to an absolute minimum.

Inside the fuselage
of every 737,

Boeing has installed
a series of tear straps.

If any kind of tear develops
in the fuselage,

it should only run
as far as the next tear strap,

never more
than 13 centimeters away,

before shooting off
at a 90-degree angle.

This would have prevented
the sort of

catastrophic disintegration
that ripped apart The Comet.

The purpose of the tear strip
is to confine any kind
of rip or tear

in the fuselage skin
to a ten inch square basically.

The ten-inch square
allows controlled decompression,

and confines
any structural damage
to a very small area.

But for Aloha 243,

the tear straps did not contain
the rupture caused
by the metal fatigue.

The NTSB believes there were
so many cracks
in the fuselage

that they eventually
joined together,

tearing an enormous hole
in the plane.

But jets aren't held together
by rivets alone.

The Comet disaster had
also highlighted the need
to reinforce the fuselage.

The skin of an airplane is built
from separate panels,
which overlap.

These panels are bonded together
by a powerful adhesive,
known as epoxy.

As the epoxy hardens,
the panels are locked together
by rivets.

And during his investigation
on the Aloha fuselage,

Jim Wildey finds discoloration
inside some
of the overlapping joints.

You can see now
where the dark material is

the epoxy that was used
to bond the two layers
of the lap joint together.

The white material you see here
is corrosion damage.

of the aluminum fuselage skin.

The Hawaiian climate
is great for tourists,

but it's tough on airplanes.

The ocean air is humid
and heavy with salt.

It can corrode even
industrial epoxy.

Investigators learned
that Boeing, the company
that built Aloha 243,

had issued
numerous written warnings
about the epoxy.

If it isn't applied
at the right temperature,

if the panels have moisture
or dirt on them,
the bonding can fail.

Boeing recommended
regular detailed inspections.

But workers
at Aloha didn't report
any problems with the epoxy.

They either never saw
the compromised epoxy or,
if they did, it wasn't repaired.

The stress that's trying to pull
one skin away
from the other skin piece,

the stresses would go
through the bonding
and not through the rivets.

Of course, as this thing
becomes disbonded,

now the rivets themselves
are loaded,

and especially
this top row of rivets.

And this is the row of rivets
we think that had
the fatigue cracking in it.

These cracks
go un-repaired,

and now you have an airplane
that is a ticking time bomb.

The fuselage
on Aloha 243 was
seriously compromised

by several factors.

Poor maintenance,
the age of the aircraft
and by the heavy tours of duty.

Since 1988,

we have come light years
in understanding this.

And we no longer leave ourselves
the tolerance that used
to be left

to airlines to just go out
and take a look
at the airplane and sign it off.

The Aloha accident was
another step towards
making passenger jets safer.

It's important to always learn
from your mistakes.

It's important to learn lessons
from that.

And that has been the case
with aeronautical engineering.

The Aloha story was
a brutal lesson
in the dangers of metal fatigue.

But it wasn't the last example
of the power of cabin pressure.

Two years later,
the industry would get
another terrifying reminder.

Ladies and gentlemen,
this is your captain speaking.

My name is Tim Lancaster.

Welcome aboard this British
Airways Flight to Malaga.

June the 10th, 1990.

British Airways Flight 5390
is leaving Birmingham, England,
for Spain.

Eighty-seven people are
on board.

Eighty knots.

Two minutes into the climb,
the flight crew switch

the flight crew switch
on the autopilot,

Captain Tim Lancaster takes off
his shoulder straps.

I went into the flight deck

to ask Tim and Alistair
what they would like to drink.

Would you gentlemen
like a tea?

Please, the usual.

Minutes later,
at 5,200 meters,

the plane is very close
to its assigned altitude.

And then, like a cork out
of a champagne bottle,

the windshield bursts
from its frame.

Captain Tim Lancaster
is sucked out of his seat

and is pinned to the fuselage
by blistering winds roaring

close to 550 kilometers an hour.

The temperature
is minus 17 degrees centigrade
and there's very little oxygen.

Co-pilot Alastair Atchison
is alone at the controls.

Ordinarily, cockpit windows
cannot budge from their frames.

The force of the air,
as the planes soars
through the sky,

pushes the windshield
onto the plane.

But on Flight 5390,
something has gone
terribly wrong.

Flight attendant Nigel Ogden
rushes in to help.

And I looked in.
The flight deck door
was resting on the controls,

and all I could see
was Tim hanging out the window.

I just grabbed him
before he went out completely.

Other flight attendants do
what they can.

Co-pilot Alastair Atchison
reduces speed
and descends quickly.

But as he slows the plane down,
the drop in wind pressure

lets the captain slide around
on the side of the plane.

All I remember
is Tim's arms flailing out.

His arms seemed
about six foot long.

I'll never forget
that his eyes were wide open.

I mean, his face was
hitting the side of the
side screen,

but he didn't blink.

And I thought to myself,
and I said to John,
"I think he's dead."

- "I think he's dead."
-

Just 35 minutes
after taking off,

Atchison gets
his jet safely back
on the ground.

But the most
unbelievable chapter
of this entire story

is the fact
that captain Tim Lancaster
survives his incredible ordeal.

But I remember watching
the windscreen

move away from the aircraft.
And then it had gone,
like a bullet.

It disappeared
into the distance.

And I was very conscious
of going upwards.

And, well, the whole thing
became completely surreal then,
as it would.

And I was aware of being
outside of the airplane.

I remember seeing
the tail of the aircraft.

I can remember
the engines going around.

And then I don't remember
much more.

Tim Lancaster
was pinned to the outside
of the plane

for over 20 minutes.

His injuries were
surprisingly minor.

Bone fractures
in his right arm
and wrist,

frostbite, and shock.

Within five months,
Tim Lancaster
was flying again.

In the immediate aftermath,
investigators have very little
to go on.

Windscreen was missing.
There was a certain
amount of blood around.

There were some minor dents
and scrapes on the fuselage,

as you'd expect,
if the window had gone past.

And, really, that was about it,

apart from a lot of papers
scattered around inside.

The maintenance log
is recovered from the plane.

Stuart Culling learns
the windscreen had been
replaced,

just hours before takeoff.

Everything okay?
- Fine.

She's just come out
of maintenance,
by the look of it.

Nothing much, though.
Just changed the windscreen.

I wanted to find out
exactly what had happened

to the aircraft
before it took off.

Early in the investigation,
the missing windscreen is found.

It contains a curious piece
of evidence.

There was something
like 30 bolts found with it,

most of which were
one size short in diameter,
one size too small in diameter.

On many planes,

windscreens are fitted
from inside the cockpit.

Internal cabin pressure pushes
against them, keeping them
in place.

But on the BAC 111,
the windscreen is bolted
from the outside.

The pressurized oxygen
inside the jet pushes out
against the windscreen.

The bolts must resist
this pressure.

There are enough of them there
that they simply can't pull out
of the structure.

But, of course,
if you then violate
the very premise of that

by putting the wrong bolts
on, all bets are off.

You're now a test pilot.

During his interview
with the ground engineer
who repaired the plane,

Culling gets a major break.

One thing that came out
was that he said,
"Oh, the old bolts

went into a waste bin
in the hangar
where he did the job.

and they may still be there."

So we rushed across
to the waste bin

and found something
like 80 discarded bolts.

The old bolts are
the proper size.

Why were smaller bolts
used to replace them?

And these are the ones
you checked
against the new ones?

- That's right. Yeah.
I took those...
- From the carousel?

It was
really excellent evidence.

Gold, as far as I was concerned.

Instead of using
the old bolts to put
the new window on,

the ground engineer decided
to replace them.

He did not check
the parts catalogue to verify

which bolt he needed
for the job.

Morning.

The bolts he chose
seemed the same,

but in fact, were just over
half a millimeter smaller.

They were too thin
to do the job.

Early in the morning,
working against the side
of a hanger,

the engineer couldn't tell
the difference.

Hours later,
the window gave way.

Faced with a challenge
they weren't trained for,

the crew still managed to pull
their plane back from the brink.

But the massive pressure
inside an airplane

doesn't need bad maintenance
to rip a jet apart.

That pressure can also find
a tiny flaw somewhere
in the design

and cause a nightmare
in the sky.

The Airbus A320,
one of the most popular
passenger jets in the sky.

Every day around the world,

thousands of passengers
board this plane.

When they do, they walk
through what would seem to be
an obvious weak spot

in the fuselage,

the door.

Any hole in the fuselage
is a potential danger,

so engineers designed
passenger doors
that can't be opened in flight.

It is virtually impossible.

I don't use
that word very easily,

but it is impossible
for a passenger

to open a plug type door
in flight.

Passenger doors are
plug-type doors.

They're built
to be slightly larger
than their frames.

When a plane takes off
and pressurizes,

the atmosphere
inside the aircraft seals
the door shut,

That door probably has
10,000 or more pounds
of pressure holding it

firmly in place
in that door frame.

And you have to pull it out
of that door frame
to get it open.

But not all doors
on an airplane
are built the same.

Even designs that seem flawless
on paper can rip apart
in the real world.

February the 24th, 1989.
Honolulu Airport.

United Airlines 811 is bound
for Auckland, New Zealand.

Expected flying time,

nine-and-a-half hours.

There are 355 people on board,
plus a full load of cargo.

The doors close on time
and the plane leaves the gate
just after 1:30 in the morning.

Tell them
we can handle 33,

- if it's available.
- Okay.

We did notice
that there were thunderstorms
a 100 miles south,

right on course,

which was rather unusual,
for that time of night.

So I left the seat belt sign on.

Captain Cronin's decision
to keep that sign on

will save lives.

As the 747 climbs
past 7,000 meters,
passengers sitting just above

and behind the cargo door begin
to hear a strange noise.

Kind of a grinding noise.

I heard a, like a thud.

- What the hell?
- And the next nanosecond,

it was pure,
unadulterated pandemonium.

The next thing I knew,
I found myself

on the stairwell

hanging onto the rungs.

And, I immediately knew it was
an explosive decompression.

Everything on the airplane
that wasn't fastened down,

tied down
or secured, became airborne.

The noise was incredible.

The 747's cargo door
had torn off,

ripping away a section
of the fuselage.

The pressurized oxygen
in the cabin shot out
with explosive force.

And, as I looked up,
that was the first time

I saw this tremendous hole
on the side of the aircraft

that was just a void.
And seats were missing.

And I immediately knew
that we had lost passengers.

Everything in front
of us was gone.

Where we were sitting,
we were about 6 inches
from the hole.

So, there was nothing in front
of us, or to the side of us.

The whole side
of the plane was gone.

Actually, our feet were
dangling out of the hole.

And I first thought
we weren't going to make it,

you know? I just didn't think
there was any hope.

The situation is desperate,
but by itself,

an explosive decompression
won't bring a plane down.

In 811, there's a whole
as big as Tulsa on the side
of this thing.

I mean,
it's an aerodynamic disruption
of massive proportions.

But if it was designed the way
we had designed things
a long time ago,

it would have unzipped.

After the door came off,

eventually,
a row of rivets held,

keeping the plane
from pulling itself apart.

But the gaping hole is putting
massive stress on the aircraft.

The flight crew needs to descend
as fast as possible.

CO-PILOT: Left right valves on.

Start dumping the fuel.

I am dumping.

Struggling to fly
their badly damaged jet,

the crew turned back
to Honolulu airport.

And all of a sudden,
we were slowing down,
slowing down.

And I said,
"Oh, my God, we've landed.
We're on ground."

Probably the best landing
I've ever made.

When we finally stopped
on the runway,

we deployed all ten chutes,

and the flight attendants
evacuated all of the passengers.

Thanks to
the experienced flight crew,
United Airlines 811

landed with everyone
on board alive.

But nine passengers
were missing,

sucked out of the plane
when the fuselage tore open,

taking with it five rows
of seats.

One of those passengers
was a New Zealander
on his way home,

Lee Campbell.

We got a phone call
from Chicago,

And they just said
that they regret to inform us

that our son was missing,
presumed dead.

In the wake
of their son's tragic death,

Kevin and Susan Campbell embark
on an international mission

to discover exactly why
the door had come off the plane.

Lee can't have died for nothing.

You know, you've got
to find out why he died.

And you've just got to make sure
that it never happens again.

Two months
after the accident,

the National Transportation
Safety Board holds
preliminary hearings.

During a break,
the Campbells take matters
into their own hands.

They remove several boxes full
of files.

So we quickly realized
we'd got

a really good set of papers
with a lot of things

that hadn't been released
to the public.

We were able to really start our
investigation in earnest
at that stage.

The unpublished documents reveal
a disturbing catalog of problems

with the 747's
forward cargo door,

going right back
to its original design.

Passenger doors are plug doors,
but most cargo doors
on jets open outward.

This increases the space
for luggage and other cargo.

As the plane gains altitude,
the pressure inside the jet

presses outwards
against the door.

To prevent the door
from opening,

Boeing had installed
what it believed
was a foolproof locking system.

What they do is they build
in multiple redundancies

to make sure the door
is properly latched

and does not open.
And you build it
into a point of law

that is extremely improbable
that the door would ever open.

The Campbell's research uncovers
two major flaws

with the 747 cargo doors.

The first involved
the locking system,

To lock the cargo doors,

electric motors turn
C-shaped latches
around pins in the doorframe.

A handle then moves arms
or locking sectors

over the top of the C-latches
to prevent them from reopening.

But on Flight 811,
the supposedly
foolproof system had failed.

Kevin Campbell built a model
of the 747 cargo door latch.

It showed the first deadly flaw
in the locking system.

Aluminum locking sectors
could not hold the C-latch
in place

if the latches started
to open on their own.

With the aluminum
locking sectors,

if the C-locks tried
to backwind open electrically,

it would just push
the locking sector out
of the way.

It just simply wasn't up
to the job
that it was designed for.

But what would cause
the C-lock to backwind?

The Campbells didn't have
the answer,

but they knew they were
onto something.

During their research,
they learned that two years
before Flight 811,

a Pan Am 747 out of Heathrow
had pressurization problems

as it climbed
to cruising altitude.

The pilot was forced
to turn back.

When they got back to Heathrow,
they found that
the door was hanging open

an inch and a half at the bottom
and all of the locks were open.

When it got
to the maintenance base,
they found that

all of the locking sectors were
either bent or broken.

The passengers
on this flight were lucky.

They had survived
the faulty locking system.

But why had the C-latches turned
and bent the locking sectors?

As the Campbells continue
to search,
a Pan Am report surfaces

that lays out a critical issue
with the cargo door's
electrical system.

When the cargo door's
outer handle is placed
in the closed position,

a master lock switch should
disconnect the power supply.

This would stop
the C-latches from turning.

But something was wrong
with the switch.

There was power
to the door locks with the...

with the outer handle closed.
And the locks started to move

and it started to force
the locking sectors out
of the way.

The faulty power switch
and weak locking sectors

were no match
for the pressurized
oxygen inside the plane.

After years of being pushed
by the Campbells,

the NTSB produces a report
that agrees.

There was an inadvertent failure
of either the switch
or the wiring

that caused
an uncommanded opening
of the door.

It's nice
that other people know

that you're right, and had been
all along.

And the support
that they had given you was,
you know, was vindicated.

I couldn't have lived
with myself if we had done
no investigating ourselves.

It was just something
we both felt

we needed to do.
We didn't even discuss it.

We just knew

that's what we would do.

After United Flight 811,

the locking system
on the Boeing 747 cargo doors
was changed.

Inspections were increased.
Another potential cause

of explosive decompression
had been found and eliminated.

That is an amazing accolade
to what we've learned,
not just Boeing,

but what we've learned
about maintenance,

about structures,
maintaining them
and inspecting them.

Since the first jet engines
pushed planes higher in the sky,

the aviation industry
has struggled to harness

and contain the deadly power
of pressurized oxygen.

They know all too well
that a single flaw can lead
to a terrifying decompression.

But more than 15 years
after United 811,

another deadly lesson
is learned.

Helios five-two-two,
do you read? Over.

It's August the 14th, 2005.

For almost an hour,

Helios Flight 522 has been
circling the skies over Athens.

Helios 522, over.

Its flight crew
has stopped communicating
with air traffic control.

Fearing a terrorist attack,
the Greek air force

scrambles two fighter jets
to circle the mystery aircraft.

One of them was

actually in a shooting position
behind

the 737.
The other one was
nearby the cockpit,

and he was trying
to communicate visually
with the person in the cockpit.

The fighter pilots
can't see any damage to the jet.

No holes in the fuselage.

There is no structural failure.
There is no fire.

There is no problem,
obvious problem,

from the external view
with the plane.

Someone in the cockpit waves
at the fighter pilot.

But all too soon,
the jet loses altitude
and falls towards the ground.

All 121 people
on board are killed.

It's the worst air crash
in the history of Greece.

Within minutes,
investigators are on the scene.

So we climbed over the hill,
and there we were. You know,

facing this situation,
which was beyond
any description.

I saw

a great area in front of me,
which was burning.
It was black,

burning, people spread,
pieces of the airplane.

The autopsies add more mystery
to the case.

Everyone on board
the Helios flight was alive
up to the moment of the crash.

He did not die from inhaling
a toxic substance

in the airplane
or from an explosion.

These people died on impact.

But if the passengers
were alive until impact,

why didn't the fighter pilots
see more activity on the plane?

Akrivos Tsolakis
is the lead investigator.

He begins to dig
through maintenance records.

He learns that
on the day of the crash,

the rear door had been
inspected for leaks.

Before it took off
on its last flight,

the Helios jet arrived
in Cyprus with a problem.

During the trip, the cabin crew
had heard loud banging

and saw ice
on a rear service door.

To make sure
there's nothing wrong
with the seal on the door,

the engineer runs
a pressurization test.

He's looking for a leak.

So explain again
how you tested the pressure?

I went into the cockpit,

I turned
the pressurization switch
to manual.

Switching digital pressure
control unit from auto
to manual.

The jet's engines
are turned off,
so the engineer uses the plane's

auxiliary power unit
to force air into the cabin.

Just like looking for a leak
in a tire.

In this case,
what you're having to do
is pressurize the aircraft,

use a barometer, essentially,
to monitor the pressure inside.

And look for leaks that way.

A normally well-maintained
jetliner of any age

is simply not going to be
completely airtight.

You're going to have leaks.
As a matter of fact, as pilots,

we know that

certain airplanes are going
to leak more than others,

and you've really got to
crank the pressurization up.

After completing
the pressurization test,

the ground engineer reports
that the jet is
in good working order.

But the digital pressure control
is left in the manual position.

They were supposed to return
the selector
to the auto position.

If the flight crew fails to see
that the switch is on manual,

their plane won't
properly pressurize.

The oxygen available
inside the plane

will be just as thin
as the outside atmosphere.

The passengers will be
directly exposed

to a deadly environment
in which they cannot survive.

August the 14th, 2005.

The worst airline disaster
in Greek history has stunned
the nation.

Investigators are sifting
through the gruesome wreckage.

A few minutes after 9:00 a.m.

Helios Flight 522 left
from Cyprus bound for Athens.

The crew has no idea
that hours before takeoff
during a maintenance test,

a flight engineer has left
a pressurization switch set
to manual.

Both the captain
and co-pilot miss the fact

that the plane is not set
to pressurize automatically.

As Helios 522 climbs,
an alarm blares in the cockpit.

What is it?

A takeoff config warning?

It's
a non-pressurization warning.

but it sounds identical
to another alarm.

The pilots confuse the two.

It's a critical mistake.

The alarm sounded.

And that alarm
was misinterpreted.

Most of

the flight crew,
they will never

face an alarm

with non-pressurization

in all their flight career
because it's a rare event.

Operations,
this is Flight 522, over.

Flight 522,
what can I do for you?

We have a takeoff
config warning on.

Sorry, can you repeat?

As the pilots troubleshoot
with ground engineers,

life-sustaining oxygen is slowly
seeping out of the plane.

Eventually, oxygen masks
drop in the cabin.

They do not fall in the cockpit.

The reason that we don't
have automatically

deploying oxygen masks
in a cockpit is

there's simply
too much up there.

And if you have things
popping out,

they're going to hit switches
that they shouldn't hit.

The crew don't realize they have
a pressurization problem.

Eventually, both the captain
and the co-pilot
collapse, unconscious.

The oxygen is too thin
to breathe.

We're the ones that

should be trained
consistently to understand

that the ears popping, anything
that indicates pressurization,

you don't even talk
to each other before you grab
that mask and put it on.

The passengers are unaware
that the plane

is now flying itself.

In emergency situations,

chemical generators
above the seats pump out oxygen.

But there's a catch.

These generators only produce
enough oxygen for
about 12 minutes.

Well, the problem
with the passenger masks is,

for one thing,
they're not designed
to keep you oxygenated

at a high altitude.
What they're designed to do,

is give you enough oxygen,

so that you can survive
until the pilots

get the airplane down
to a low altitude.

But with both pilots
already unconscious,

the Helios jet did not descend
so passengers could breathe
without assistance.

Instead, the plane flew
on autopilot to Athens.

When the oxygen supply stopped,
the passengers passed out.

By the time the Greek Airforce
intercepted the Helios jet,

only one person was
still moving.

Likely surviving
with bottled oxygen,

flight attendant
Andreas Prodromou

was still conscious
when the fighters approached.

He made it to the cockpit,
but he couldn't save the plane.

Athinai control.

There is one person moving
in the cockpit
of Helios 522.

Eventually,
when its fuel ran out,

Helios 522 crashed.

Investigators eventually find
the panel
with the pressurization switch.

Are you sure
this is the way it was found?

It hasn't been moved at all?

All 121 people
on the Helios flight died

because their plane didn't carry
enough life sustaining oxygen
as it climbed into the sky.

It's been more than 50 years
since the beginning
of the passenger jet era,

fifty years in which the
industry has learned,
sometimes painfully,

how to safely fly
more than ten kilometers
in the sky.

When you look back
at all the other accidents
over the last 20 years,

in most cases, we were pushing
the frontier of knowledge.

Unfortunately, when you're
pushing the envelope,

you're pushing the boundaries
of design.

You're going
to encounter problems
that you hadn't anticipated.

In search
of the safest plane imaginable.

The history of aviation
traces a flight path

through tragic accidents
to technological breakthroughs.

Many of these accidents
display the incredible power

of explosive decompression.

The Airbus A320 and every other
passenger plane built today

is infinitely safer
than the first jets
that flew in the 1950s.

They have to remain safe
and get even safer,

because we rely so heavily
on this incredible mode
of transportation

that takes us somewhere
we were never meant to be.