All language subtitles for Air Disasters S18E22 Ripped Apart 1080p PMTP WEB-DL DDP5 1 H 264-maldini_track3_[eng]

NARRATOR: Every passenger jet
is a traveling life support

system filled with
highly pressurized oxygen

to keep us alive.

If the oxygen 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.

NARRATOR: Aloha 243.

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

NARRATOR: 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!

NARRATOR: 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.

FLIGHT ATTENDANT (ON INTERCOM):
Ladies and gentlemen,

we are starting our approach.

PILOT: We lost both engines.

PILOT: Mayday.

Mayday.

WOMAN: Brace for impact!

MAN: He's gonna crash!

NARRATOR: This is the assembly
plant for the Airbus A320.

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

More than 9,000
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 half

an inch 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.

JOHN NANCE: 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 that air stream

out there would kill
you almost immediately.

NARRATOR: It's not
natural for people

to travel through this
killer atmosphere.

But every day, millions of us
fly almost 10,000 feet 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.

NARRATOR: But taking oxygen
with us up to 36,000 feet

is potentially dangerous.

The air inside an airplane
is pressurized so passengers

can breathe easily.

As the 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 yard

of the fuselage must support
almost 6,000 pounds of force.

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

but only because
airplane designers

have learned tragic lessons.

In the 1950s, a series
of shocking accidents

led to modifications that
are still seen today.

ANNOUNCER: The Comet
has blazed new trails,

achieving new speeds,
setting a new standard.

NARRATOR: The passenger
jet era began in the 1950s

in Great Britain,
with the introduction

of the de Havilland Comet.

For the first time, jet engines
took commercial planes higher

than they'd ever gone before.

JAMES DELAURIER: 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.

NARRATOR: But less than two
years after its maiden flight,

the glittering jewel
of British aviation

disintegrated in mid-air.

JAMES DELAURIER: It
would have been horrible,

but mercifully it
would have been quick.

What they had found with the
bodies that they had recovered

is 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 many of these people
actually smashed their heads

against the structure.

NARRATOR: Three months
later, another Comet

ripped apart in flight.

Officials feared that
every single Comet

was a flying time bomb.

The entire fleet was 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.

NARRATOR: Unknown to engineers,
there was a deadly flaw

in the Comet's 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 flight.

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 traveled rapidly

through the rest
of the structure

causing a massive decompression.

NARRATOR: 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.

NARRATOR: Every plane
that's built today

is safer because of
the Comet disasters.

Like other passenger planes,
the windows in the A320

are rounded so that
pressure doesn't

build up around the corners.

Perhaps even more important--
extra rivets reinforce the skin

of today's planes to
contain cracks that might

start anywhere on the fuselage.

This Airbus factory
in Toulouse, France

rolls out one new A320 just
about every working day.

A big part of the
job is strengthening

the fuselage with lightweight
and extremely tough

titanium rivets.

3,000 rivets join the
separate sections together.

Another 3,000 are
used 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 28, 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 Aloha's planes.

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.

NARRATOR: 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.

JAMES DELAURIER: There's
an internal structure

to a modern all metal airplane.

The skin without the structure
would collapse easily.

It would buckle easily.

It'd be sort of like a--

you know, a paper
bag without the--

without any structure
inside to hold it.

NARRATOR: Beneath the
skin of a passenger jet,

hoop shaped
bulkheads and formers

support the aircraft's width.

Stringers run the
length of the plane,

further helping to
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 inch.

Passengers aboard Aloha
243 are about to learn

what happens when that
pressurized air suddenly

escapes.

NARRATOR: April 1988--

Aloha Flight 243 is
en route to Honolulu

when the plane rips open.

I saw a brilliant flash
of light, then boom.

Everything was going--

was being sucked
out of the plane.

NARRATOR: Aloha Airlines 243 has
just suffered what experts call

an explosive decompression.

The air inside the plane escapes
in a sudden horrifying moment.

370 square feet 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 into that cabin.

That's three times
hurricane force winds.

Those people were dressed for
Hawaii in the springtime, not

minus 50 degree temperatures.

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

What was that?

We have to get down!

NARRATOR: Captain
Bob Schornstheimer

begins an emergency descent,
dropping 75 feet a second.

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

The woman that was
sitting next to me--

her husband, he was on the
other side in the next row up.

She was next to me.

And they were reaching
their hands out,

and they were trying to
touch fingers to say goodbye.

NARRATOR: 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.

In 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.

A plane isn't a rigid 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.

So the airplane is
constantly cycling.

That's pressurization.

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

NARRATOR: Records show that
the Aloha jet was 19 years old.

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?

NARRATOR: 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.

NARRATOR: But something
doesn't make sense.

The Aloha jet lost 370
square feet of its fuselage.

In the years after
the Comet disaster,

Boeing and other
companies designed

a safety feature meant to
keep any tearing to a minimum.

Inside the fuselage
of every 737,

Boeing installed a
series of tear straps.

If a tear develops
in the fuselage,

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

never more than
five inches away--

before being redirected.

This is meant to prevent the
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 10-inch square,

basically.

The 10-inch square allows
a controlled decompression

and confines any structural
damage to a very small area.

NARRATOR: But on Aloha
243, the tear straps

did not contain the rupture
caused by the metal fatigue.

The NTSB believes that the
many cracks in the fuselage

eventually joined
together, allowing

an enormous hole to open
under the stress of flight.

But jets aren't held
together by rivets alone.

The Comet disaster
had also highlighted

the need for redundancy.

The skin of an airplane is
built from separate overlapping

panels.

These panels are bonded
together by a powerful epoxy.

Then the panels are
locked together by rivets.

During his investigation
of the Aloha fuselage,

Jim Wildey defines
discoloration inside some

of the overlapping joints.

You can see it 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.

NARRATOR: 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
warnings about the epoxy.

If it isn't applied at
the right temperature--

if the panels have
moisture or dirt on them--

the bonds 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 unrepaired,
and now you have an airplane

that is a ticking time bomb.

NARRATOR: The
fuselage on Aloha 243

was seriously compromised
by several factors--

age, poor maintenance,
and 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.

NARRATOR: The Aloha accident
was another step toward 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.

NARRATOR: Aloha 243 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.

PILOT (ON INTERCOM):
Ladies and gentlemen,

this is your captain speaking.

NARRATOR: June 10, 1990--

British Airways Flight 5390 is
leaving Birmingham, England for

Spain with 87 people on board.

80 knots.

NARRATOR: Two minutes into
the climb, the flight crew

switches on the autopilot.

Captain Tim Lancaster
removes his shoulder straps.

I went into the flight
deck to ask Tim and Alastair

what they would like to drink.

You gentlemen like a tea?

Please, the usual.

NARRATOR: Minutes
later, at 17,000 feet,

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

more than 340-miles-an-hour.

The temperature is just above
zero degrees Fahrenheit,

and there's little oxygen.
Co-pilot Alastair Atchison

is alone at the controls.

Ordinarily, cockpit
windows cannot budge.

The force of the
air as the plane

soars through the sky
presses the windshield

against the fuselage.

But on Flight 5390, something
has gone terribly wrong.

Flight attendant Nigel
Ogden rushes in to help.

NIGEL OGDEN: When I looked
in, the flight deck door

was resting on the controls.

And all I could see
was Tim out the window.

I just grabbed him before
he went out completely.

NARRATOR: 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.

NIGEL OGDEN: All I remember
is Tim's arms flailing out.

His arms seemed
about 6-foot long.

And 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 said, I think he's dead.

I think he's dead.

NARRATOR: Just 35
minutes after taking off,

Atchison gets the jet
safely back on the ground.

But in the most unbelievable
chapter to end this story,

Captain Tim Lancaster
survives the horrific 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 can remember seeing
the tail of the aircraft.

I remember the
engines going around.

And-- and then I don't
remember much more.

NARRATOR: Tim
Lancaster was pinned

to the outside of the plane
for more than 20 minutes.

His injuries were
surprisingly survivable--

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 paper

scattered around inside.

NARRATOR: The maintenance log
is recovered from the plane.

Stuart Culling learns the
windscreen had been replaced

just hours before takeoff.

Early in the investigation, the
missing windscreen is found.

It contains important evidence.

There were something like
30 bolts found with it,

most of which were one size
short in diameter, one size

too small in diameter.

NARRATOR: During his
interview with a ground

engineer who repaired the plane,
Culling gets a major break.

STUART CULLING: 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 he rushed across
to the waste bin

and found something
like 80 discarded bolts.

NARRATOR: The old bolts
are the proper size.

Why were smaller bolts
used to replace them?

These are the ones you
checked against the new ones?

That's right.
Yeah.

I took those off.
- From the carousel?

Yeah.

STUART CULLING: This was really
excellent evidence-- gold,

as far as I was concerned.

NARRATOR: Instead of
using the old bolts

to put the new window on, the
ground engineer replaced them.

He did not check the parts
catalog to verify which

bolts he needed for the job.

Morning.

NARRATOR: The bolts he
chose looked similar,

but were 0.2 inches
or 20% smaller.

They were too thin
to do the job.

Early in the morning, working
in the shadow of a hangar,

the engineer couldn't
tell the difference.

Hours later, the window
gave way under the force

of the pressurized
air inside the plane.

Faced with a challenge
they weren't trained for,

the crew still managed
to avoid disaster.

5390!

NARRATOR: 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.

NARRATOR: The Airbus A320--

one of the most
popular passenger jets.

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.

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.

NARRATOR: 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 24, 1989,
Honolulu Airport.

United Airlines 811 is bound
for Auckland, New Zealand.

Expected flying time--

9 and 1/2 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.

OK.

DAVID CRONIN: We did notice
that there were thunderstorms

100 miles south, right on
course, which was rather

unusual for that time of night.

So I left the seatbelt sign on.

NARRATOR: Captain
Cronin's decision to keep

that sign on will save lives.

As the 747 climbs
past 2,300 feet,

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?

The next thing I knew, I found
myself on the stairwell hanging

on to 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.

NARRATOR: 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.

BOB BAHNA: 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 on the hole,

and my first thought, we
weren't gonna make it.

You know, I just didn't
think there was any hope.

NARRATOR: The
situation is desperate.

An explosive decompression won't
bring a plane down by itself,

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

The flight crew needs to
descend as fast as possible.

Left-right valves on.

Start dumping the fuel.

I am dumping.

NARRATOR: 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.

DAVID CRONIN: Probably the
best landing I've ever made.

When we finally
stopped on the runway

we deployed all 10 chutes,
and the flight attendants

evacuated all the passengers.

NARRATOR: 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 apart, 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.

NARRATOR: 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.

Two months after the
accident, the National

Transportation Safety Board
holds preliminary hearings.

During a break, the
Campbells remove

several boxes full of files.

SUSAN CAMPBELL: So
we quickly realized

we had 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

and learn most at that stage.

NARRATOR: The
unpublished documents

reveal a disturbing
catalog of problems

with the 747's
forward cargo door,

going back to its
original design.

Unlike doors for passengers,
most cargo doors open outward.

This increases the space
for luggage and other cargo.

The Campbell's research uncovers
two major flaws with the 747

cargo door locking system.

To lock the cargo
doors, electric motors

turn C-shaped latches around
pins in the door frame.

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 system had failed.

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

It showed the first deadly
flaw in the locking system.

The aluminum locking sectors
did not hold if the C latches

started to open on their own.

With the aluminum
locking sectors--

if the C locks tried to back
wind, 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.

NARRATOR: During their
research, the Campbells

learned that two years before
Flight 811, a Pan Am 747 out

of Heathrow was
forced to turn back

when its cargo doors
opened and prevented

the cabin from pressurizing.

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.

NARRATOR: The passengers
on this flight were lucky.

They survived the
faulty locking system.

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

As the Campbells
continued 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 closed,

a master switch is supposed
to disconnect the power supply

and 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 lock started
to move, and it

started to force the locking
sectors out of the way.

NARRATOR: 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
will know that you're right,

and had been all along,
and that the support

that they had given you was--
you know, was vindicated.

SUSAN CAMPBELL: 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.

NARRATOR: After
United Flight 811,

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

Inspections were increased.

Another potential scenario
for explosive decompression

had been found and eliminated.

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.

And more than 15 years
after United 811,

another deadly
lesson is learned.

Helios 522, do you read?

Over.

NARRATOR: August 14, 2005--

for almost an hour,
Helios Flight 522 has been

circling the skies over Athens.

AIR TRAFFIC CONTROL:
Helios, 522, over.

NARRATOR: 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.

FAITHON KARAIOSOFIDES:
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.

NARRATOR: 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.

NARRATOR: 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.

I saw a great area in front
of me, which was burning.

It was black, burning,
people spread, pieces of--

of the airplane.

NARRATOR: The autopsies add
more mystery to the case.

Everyone on board the
Helios flight was alive up

to the moment of the crash.

INTERPRETER: They did
not die from inhaling

a toxic substance
in the airplane,

but from an explosion.

These people died on impact.

NARRATOR: 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 in Cyprus.

After landing in
Cyprus, the cabin crew

reported the problem.

They had heard loud
banging and saw

ice and the rear service door.

To make sure there's
nothing wrong with the seal

on the door, an 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.

NARRATOR: The jet's
engines are turned off,

so the engineer uses the
plane's auxiliary power unit

to force air into the cabin.

BILL WALDOCK: It's 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.

NARRATOR: 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.

NARRATOR: Both the
captain and co-pilot

missed 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 take-off config warning?

NARRATOR: It's a
non-pressurization warning,

but it sounds identical
to another alarm.

The pilots confuse the two.

It's a critical mistake.

FAITHON KARAIOSOFIDES: The
alarm sounded, and that alarm

was misinterpreted.

Most of flight crew,
they will never

face an alarm with no
pressurization in all

their flight career.

Because it's a rare event.

PILOT (ON RADIO): Operations,
this is Flight 522.

Over.

Flight 522, what
can I do for you?

We have a take-off
config warning on.

Sorry.

Could you repeat?

NARRATOR: 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-- there's simply

too much up there.

And if you had
things popping out,

they're gonna hit switches
that they shouldn't hit.

NARRATOR: The crew
don't realize they

have a pressurization problem.

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

unconscious from
a lack of oxygen.

We're the ones that should
be trained consistently

to understand that
ears popping--

anything that indicates
pressurization,

you don't even talk to
each other before you

grab that mask and put it on.

NARRATOR: The passengers
are unaware there

is no one at the controls.

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't survive until
the pilots get the airplane

down to a low altitude.

NARRATOR: But with both
pilots already unconscious,

the Helios jet does not
descend so passengers

can breathe without assistance.

Instead, the plane flies
on autopilot to Athens.

When the oxygen supply stops,
the passengers pass out.

By the time the Greek Air Force
intercepts the Helios jet,

only one person is still moving.

Likely surviving with bottled
oxygen, flight attendant

Andreas Perdomo
is still conscious

when the fighters approach.

He makes it to the cockpit,
but he can't save the plane.

FIGHTER PILOT (ON
RADIO): Athens control,

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

NARRATOR: Eventually,
when its fuel runs out,

Helios 522 crashes.

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?

NARRATOR: 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--

50 years in which the industry
has learned, sometimes

painfully, how to
safely fly more

than six miles up in the sky.

Unfortunately, when
you're pushing the envelope

and you're pushing the
boundaries of design,

you can encounter problems
that you hadn't anticipated.

NARRATOR: 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.