Original subtitles

Man: Cleared for takeoff for Tahiti, runway 1-2.

Narrator: One of the most rugged planes ever built...

Man: Pilots all called it the Jeep In The Sky.

Narrator: ...crashes into the sea near Tahiti.

Man: A plane doesn't just crash for no reason.

Narrator: Air traffic controllers

have no idea what happened.

Controller: We're a small airport here.

We're not equipped with radar.

Man: It looked like it was going to be

a very difficult investigation.

Narrator: Was it a medical emergency?

Man: The pilot might have had a physical breakdown.

Narrator: An act of sabotage?

Man: No!

Narrator: Or something even more alarming--

a hidden threat that lurks at commercial airports

around the world?

Flight attendant: Ladies and gentlemen, we are starting our approach.

Pilot: We lost both engines!

Flight attendant: Put the mask over your nose.

Emergency descent.

Pilot: Mayday, mayday.

Flight attendant: Brace for impact!

Controller: I think I lost one.

Man: Investigation starting...

Man: He's gonna crash!

Narrator: Pilot Michel Santurenne

cruises low over the islands of French Polynesia.

Michel Santurenne: Air Moorea requesting clearance

for approach, runway 1-2.

Narrator: It's one of up to 40 flights a day

between the islands of Moorea and Tahiti.

Controller: Air Moorea, you are cleared for final.

Runway 1-2.

Narrator: It's a route Eric Limore knows well.

Eric Limore, translated: Moorea is an island

that's really close to Tahiti.

The distance between them isn't even 20 kilometers.

There's just the channel to cross.

Narrator: Tahiti and Moorea are two

of more than a hundred islands that make up French Polynesia,

halfway between Australia and South America.

Pristine beaches and lush mountain peaks

attract thousands of tourists a year.

Air Moorea specializes in the short flights

that provide a vital link between the islands.

Limore: Air Moorea and its planes were really part

of the daily landscape for the Polynesians--

people working in Tahiti and living in Moorea--

and for the tourists.

It really was the quickest and most efficient link.

Santurenne: Me again.

Narrator: Michel Santurenne joined Air Moorea

just three months ago.

Santurenne: I'll take the passenger list and load sheet

if it's ready.

Narrator: After a career in the military,

he's beginning a new life in paradise.

Limore: He had taken care of everything

to welcome his family.

His wife was joining him soon.

Santurenne: Ah, another full one.

Just the way we like it.

Narrator: Santurenne flies these short hops on his own,

with no co-pilot or cabin crew to help out.

Santurenne: Ok.

Time to fly.

No time to waste in paradise.

Narrator: Every 30 minutes he needs to be ready

for another takeoff.

Limore: The captain would quickly check the plane

to see if there was anything alarming, a deflated tire,

anything that might call their attention.

Narrator: The twin otter turboprop

is a rugged 19-passenger aircraft built in Canada.

Limore: In fact, we pilots all called it the jeep in the sky.

Santurenne: Nice shirt.

Limore: We would greet the passengers quickly and reboard.

It was very, very short, let's say.

Man: How are you doing?

Santurenne: Just put the luggage in the seat in front of you.

A beautiful day to fly.

Narrator: After less than 15 minutes on the ground,

Santurenne is ready to go again.

Santurenne: Tower, we're ready to taxi.

Controller: Air Moorea, you are cleared for takeoff, runway 1-2.

Santurenne: Cleared for takeoff for Tahiti, runway 1-2.

Narrator: The twin otter has little automation.

Santurenne flies this plane by hand.

Limore: The majority of modern commercial planes

are loaded with help for the pilots--

electronics, screens--

but on this type of plane,

you have the pleasure of handling the plane

and fully controlling it.

Narrator: At this island airport,

the ocean is just off the edge of the 1,300-yard runway.

Limore: When we fly over there, it's magical--

blue lagoons, magnificent islands,

the greenery, the mix of colors--

it's certainly paradise.

Narrator: Vacationers get to watch

the regular takeoffs and landings.

The flight is one of the shortest on earth--

just seven minutes from takeoff to touchdown.

Santurenne: Huh?

Damn it!

Narrator: But on flight 1121, something is wrong.

The twin otter is losing altitude fast.

Woman: Oh, my god!

Narrator: It falls into a steep dive.

Less than two minutes after takeoff,

flight 1121 crashes into the pacific.

Woman: Oh, my god!

Woman: Look!

Narrator: The tower is told what people have seen.

Controller: Is it floating or has it gone under?

Narrator: Local fishermen rush to help.

But they find no survivors, only bodies.

All 20 people on the flight are dead.

Limore: I will always remember.

It was terrible, because we were still hoping

that despite what happened, people would come out alive,

or at least a couple.

Narrator: The disaster touches nearly everyone

in the tiny island community.

Limore: In Polynesia everyone knows each other.

Everyone is someone's cousin or knows their family,

so people were hit very hard by this accident.

Narrator: The Air Moorea fleet is grounded

when pilots refuse to fly the twin otter

until they know what caused the crash.

Limore: A plane doesn't just crash for no reason.

It was either due to pilot error or a mechanical problem.

So before continuing to fly,

we asked that the whole fleet be checked out.

Man: Bonjour.

Narrator: Because Moorea is a French territory,

a team from France's accident investigation bureau,

the B.E.A., is sent from Paris.

It's their job to figure out what went wrong.

Alain Bouillard: Tell me there's more.

Narrator: Alain Bouillard leads the investigation.

Bouillard, translated: The twin otter was an extremely robust plane

that was used in all the difficult places

where other planes can't normally take off and land.

That made us wonder, what could have happened to this plane

that would have made it hit the water?

Narrator: Investigators usually rely on clues from the wreckage.

Bouillard: This tells us nothing.

Narrator: But most of this plane is at the bottom of the ocean.

Bouillard will have little to go on

unless he can get vital pieces back on dry land.

Bouillard: We are going to need a lot more wreckage than this.

Narrator: There's another reason to find the plane.

Unlike large airliners,

twin otters are not required to carry cockpit voice recorders.

But Air Moorea installed one anyway.

It could hold the answers investigators are looking for.

Arnaud Desjardin: We were hoping to get,

in addition to the voice in the cockpit voice recorder,

any kind of alarms that would sound.

Narrator: But recovering the CVR from the deep waters

off the coast of Moorea will be a huge challenge.

Desjardin: Way too deep to send down divers.

The sea depth at this area was around 700 meters,

so obviously, we cannot send any diver.

You need to send

a remote control-operated submarine.

Narrator: Investigators arrange for a ship

equipped with a remote-controlled submersible

to assist in the recovery-- the ile de re.

There's just one catch--

it's more than 2,400 miles away off the island of New Caledonia.

It could take weeks for the ship to get to Moorea.

Flight 1121's CVR is equipped with a locator beacon,

or pinger, but the battery that powers it

will only last 30 days.

Desjardin: We tried to send that recovery ship

as soon as possible

and within the 30 days of the battery life of the pinger.

Bouillard: It looked like it was going to be

a very difficult investigation

if we couldn't recover the cockpit voice recorder.

Narrator: Meanwhile, investigators talk

to the controller at the airport.

A radar track could provide some clues

about what brought the plane down.

Desjardin: The first evidence that we like to get

when the investigation starts, of course,

is a sense of the trajectory,

the last departure point and the impact point.

So we try to get this type of information.

Narrator: But they're not going to get what they hope for.

Controller: We're a small airport here.

We're not equipped with radar.

Narrator: It's yet another setback.

Desjardin: When we discovered

that we did not have any radar data,

we were slightly disappointed

in the sense that we knew it was going to be harder

to recreate the trajectory of the aircraft.

Woman: I saw the plane climbing,

and then suddenly it dove into the water.

Narrator: Until the ile de re arrives,

investigators must rely on the only evidence they have--

witness reports of the crash.

Bouillard: We thought it was critical

to gather all the eyewitness accounts

to help us understand what happened.

Desjardin: Most of the witnesses were either on the beach

in Moorea, or on the boats, fishing.

All of them stated that they saw the aircraft climbing normally.

Narrator: Every day more than 500 twin otters navigate

some of the most challenging routes on earth--

from the Australian outback

to the frozen tundra of the far north.

If there's a fatal flaw in the famously sturdy twin otter,

the aviation world needs to know as soon as possible.

Investigators are under pressure

to figure out what brought down flight 1121.

Bouillard: He was climbing normally,

then seems to lose control of the plane.

Maybe it was their weight?

Desjardin: When you have a weight imbalance issue,

you usually have your troubles right after takeoff.

Narrator: Correctly calculating the weight of cargo, passengers and fuel

is critical on small commuter planes.

Getting it wrong can be deadly,

as a crash in the United States demonstrated in 2003.

U.S. Airways Express flight 5481

departs from Charlotte, North Carolina.

Just 30 seconds after takeoff

the pilots lose control of their beechcraft 1900.

The commuter plane plummets to the ground,

hitting an airport hangar and killing all 21 people on board.

Investigators discover the plane was dangerously overloaded--

more than 550 pounds over

its maximum allowable takeoff weight.

The crew used incorrect estimates

for passenger and baggage weight.

Desjardin: It's very important to know the weight

of your aircraft before you take off.

And therefore, we did investigate this issue

very, very soon into the investigation.

Bouillard: 19 passengers with fuel and cargo.

Narrator: The B.E.A. Team checks the load and balance sheets

from the air Moorea flight and finds no issues.

Desjardin: We found out that everything was within

the manufacturer's limits.

Bouillard: They should have been fine.

Narrator: Whatever brought down the plane,

it had nothing to do with weight.

Until help arrives to search

for the plane's sunken cockpit voice recorder,

there is no more evidence to go on.

Bouillard decides to take a chance on an unusual tactic

to try to figure out what went wrong.

Bouillard: I need a small plane and a good pilot.

Merci.

Narrator: Above the island of Moorea,

Alain Bouillard takes an unusual flight

aboard a small commuter plane--

a flight he hopes will enhance the memory

of those who witnessed the crash of flight 1121.

Bouillard: Ok, let's make a pass over the lagoon.

Narrator: Pilots have a specific task to do

at each stage of the flight.

If witnesses can identify how high santurenne climbed,

it might help investigators figure out

what he was trying to do when he lost control of the plane.

They ask witnesses to watch

as Bouillard's plane climbs from the airport.

Desjardin: If you ask them what was the maximum altitude,

they might not be able to tell you,

oh, this was 500 feet or 1,000 feet or 2,000 feet.

But if you actually show them an aircraft in the air,

and say, this is 500 feet.

Did it match what you saw?

They can say more easily, yes or no.

Woman: No, it's too high.

Bouillard: Ok, let's make one more pass,

this time a little lower.

Desjardin: We asked the witnesses to tell them

which one of the recreated flights matched the most

what they remember from the day of the accident.

Woman: Yes, that's exactly where I saw the plane.

Man: The right height.

Bouillard: Excellent.

We're at an altitude of almost 400 feet.

Ok. Let's go back.

Narrator: The test flights give Bouillard a good idea

of how high Michel santurenne managed to climb.

Bouillard: The flights we did allowed us to estimate

the altitude at which the plane changed its trajectory.

Whatever went wrong, it happened when he was still climbing.

Narrator: But he still doesn't know

what caused the plane's sudden dive,

or why the pilot couldn't recover.

Desjardin: When you have an airplane going nose-down

after takeoff, you can think of engine failure, obviously.

Dual engine failure.

Narrator: A twin otter can fly safely with only one engine.

But if both engines fail, that could cause a steep dive

like the one the witnesses saw.

Desjardin: That was a possibility.

It would match, in terms of trajectory.

Narrator: But having two engines fail at the exact same time

is an extremely rare event.

Desjardin: Dual engine failure could be caused, of course,

by fuel starvation,

but that's quite unlikely right after takeoff.

Or, it can be also, let's not forget bird ingestions

in both engines, but that's quite unlikely also.

Narrator: Most witnesses also report hearing engines

as the plane dove towards the sea.

Dual engine failure now seems even more unlikely.

Sounds captured by the cockpit recorder

could confirm if the engines were running.

But until it's recovered,

Bouillard only has the unusual flight path to go on.

Bouillard: This information was certainly important,

but it didn't explain what happened.

It seemed to us that the pilot might have had

a physical breakdown,

some kind of incapacitation that put the plane into a descent.

These are planes that are flown by a single pilot.

When a pilot is physically incapacitated,

there's no one to take over control of the plane.

Desjardin: If the pilot had been incapacitated,

and then would have just, you know,

leaned over on the flight controls,

indeed it would then match the trajectory of the aircraft.

Narrator: The captain's body has been recovered

and sent for autopsy.

The coroner checks for any signs of a medical condition

that might interfere with the captain's ability to fly.

But when Bouillard reads the results...

Bouillard: It wasn't a heart attack.

Narrator: ...he's back at square one.

Limore: There was nothing to suggest

that he had a health problem.

We have regular medical checkups.

He passed without any difficulty.

Bouillard: We closed the door on pilot incapacitation

as the cause of the accident.

Narrator: Bouillard must consider every possible cause

for the crash.

He explores a terrifying possibility.

Bouillard: What about a deliberate act of sabotage?

Narrator: Did someone board the flight

intending to commit murder?

Bouillard: Intrusion into the cockpit,

it's something that was plausible.

Narrator: Bouillard knows that it's happened before.

December 7, 1987.

A disgruntled airline employee smuggles a handgun

aboard Pacific Southwest Airlines flight 1771.

In mid-flight he shoots his former boss,

then rushes towards the cockpit,

where he shoots a flight attendant and both pilots.

He then forces the plane into a steep dive.

There's no hope for any of the 43 people on board.

The small jet slams into a california hillside

and disintegrates.

Santurenne: I'm sorry, sir, you can't be...

What? What are you doing?

Narrator: If someone on Air Moorea flight 1121

entered the cockpit and attacked the pilot,

the sound of the struggle

would be on the cockpit voice recorder.

Bouillard: At this stage of the investigation,

it was pretty obvious that we had to find the CVR.

Narrator: On August 26th, 17 days after the accident,

the French research vessel ile de re finally arrives.

The team knows the approximate location of the wreckage,

but ocean currents may have shifted the sunken debris.

Desjardin: We had narrowed down the search zone

to a circle of about 260 meters in diameter.

We were fairly confident it was going to be in that zone,

but we didn't know if it was gonna be

laying by itself on the seabed,

or if it was still in the fuselage of the aircraft.

Narrator: They zero in on the recorder's locator beacon.

Bouillard: That's the sound we're looking for.

Narrator: Technicians on the ile de re

launch a remotely operated underwater vehicle, or rov,

towards the sound.

Bouillard: We quickly we located the area on the sea floor

where the wreckage was dispersed.

There's our twin otter.

Narrator: The remains of Air Moorea flight 1121

lie more than 2,000 feet below the waves.

Bouillard: We saw the detached wings.

We saw the engines.

We saw part of the cockpit.

See if you can find the tail.

The decision was quickly made to focus on the tail,

where the cockpit voice recorder could be found.

Ok, let's cut it open and get the CVR out of there.

We decided to cut through the fuselage

to recover the flight recorder.

Narrator: It's a delicate operation.

One false move, and the sub could damage or destroy

the crucial recorder.

Bouillard: Nice and easy.

Desjardin: We were really hoping to find it there undamaged,

or just slightly damaged,

and therefore increasing our chance of success

for the readout process.

Narrator: The salvage operation demands incredible patience.

Bouillard: This job of cutting out,

or of the rov chewing open a hole in the plane

took five or six hours of work

before we could get to the cockpit voice recorder.

Narrator: Finally the team frees the CVR.

Bouillard: We got it.

Excellent work.

We felt a great sigh of relief.

Desjardin: So it was a sense of satisfaction,

and then also worries, because if you have the recorder,

that's a very good thing,

but then you have to have the data in it.

So the next phase to organize

was shipping the recorder back to the lab at the B.E.A.

For a readout as soon as possible.

Narrator: Along with the voice recorder,

the salvage effort brings up other key pieces of wreckage.

Bouillard: We decided to recover some of the pieces

that we thought would be needed

in addition to the information from the CVR.

Desjardin: We wanted to get the engines.

We wanted to get as much cockpit panel as possible.

Narrator: They quickly download the CVR data.

A lone pilot hardly speaks at all.

Investigators must listen for other sounds

that could provide leads.

Desjardin: On the cockpit voice recorder

we could hear the normal takeoff roll,

and then the climb phase seems to be rolling normally.

Narrator: They can hear the sound of the plane

as santurenne lifts off and adjusts his controls.

Bouillard: An intrusion into the cockpit

was still an open hypothesis.

We waited for the CVR to close that door.

Narrator: There's no sound of an intruder in the cockpit.

Bouillard: The first impression we got from listening to the CVR

was that there was no intrusion into the cockpit,

there had been no other people in the cockpit.

Narrator: Then they hear the pilot cry out in surprise.

Santurenne: Damn it.

Bouillard: Everything was perfectly normal,

until the moment when the pilot swore.

Narrator: The sound recorded in the cockpit

allows investigators to rule out another theory as well.

Desjardin: The engines sound fine.

The CVR proved they are at their maximum takeoff power

all the way to impact.

It sounds like he's pulling in the flaps.

Narrator: The pilot's cry of surprise

comes just after he adjusts the flaps on his twin otter.

Desjardin: Again, please.

You could hear on the CVR the flap being retracted.

You can also hear the pilot breathe a little bit heavier,

like he was pulling on the flight controls at that time.

And then immediately after that,

we hear him being very surprised.

Santurenne: Damn it.

Narrator: Moments later, the plane slams into the sea.

Desjardin: Even with a lot of experience,

cockpit voice recorders always are hard to hear,

especially when you know there's a tragic, tragic ending.

It's connected to the flaps.

Just, I don't understand how.

Narrator: Investigators learn that on flights to Tahiti,

twin otter pilots retract their flaps

when they reach about 400 feet--

the same altitude where flight 1121 began to dive.

They wonder if the flaps malfunctioned.

Before takeoff, pilots routinely extend their wing flaps

to increase lift while they climb.

Limore: Once the plane approaches cruising altitude,

extended flaps increase drag.

So pilots must retract them when they approach cruising altitude.

Narrator: Investigators study the mechanism

that operates the flaps.

Desjardin: We did recover the flap actuator,

and we were able to analyze it.

Narrator: They find that it's in the correct position

and shows no sign of any malfunction.

Bouillard: Flaps are fine.

Desjardin: The results of the examination showed

that the flaps were retracted at impact.

Narrator: After weeks of work, Bouillard still can't explain

why flight 1121 fell out of the sky.

Bouillard: Now let's take a good, close look

at these cables.

Narrator: He focuses on the cables that operate

crucial control surfaces in the tail of the plane.

Bouillard: We were left with the possibility

of a mechanical breakdown or failure.

Narrator: The control surfaces in the tail of a twin otter

are activated by just four cables.

Two move the plane's rudder right and left,

and two move the elevator up and down.

All four were damaged in the crash.

Bouillard looks for anything that might tell him

when and how they snapped.

Aviation cables are made up of multiple strands of thin wire

that are twisted and then braided together

for extra strength.

Three cables have unraveled--

clear indication that they were ripped apart suddenly on impact.

Bouillard: Impact damage.

Narrator: But one cable looks different.

Bouillard: Now, this, this is interesting.

This one did not snap on impact.

Desjardin: One cable was broken in a different manner

than the three other ones.

So that was something that we had to investigate.

Narrator: Two cables run to the elevator on the tail.

One pulls it down to pitch the nose down.

The other cable pulls it up to pitch the nose up.

That's the one that broke before impact.

If it snapped in flight,

the plane would have been thrown into a severe dive.

Santurenne: Damn it.

Bouillard: The failure of the pitch-up cable

was consistent with the trajectory

that was described by the eyewitnesses.

Narrator: Finally investigators understand why

Michel santurenne lost control of his twin otter--

an extremely rare mechanical failure

that came without warning.

It's a revelation that leads to a more urgent question.

Bouillard: Ok, let's send these to Estelle in Paris

and see what she thinks.

Narrator: They must now figure out why the cable snapped

before it happens to someone else.

When the pitch-up cable arrives in Paris,

materials specialist Estelle Bancharel

examines it closely.

She sees something strange.

The cable shows clear evidence that different strands broke

at different times and for different reasons.

Estelle Bancharel, translated: The external strands were worn,

and those on the inside were not.

They had snapped.

Narrator: Distinctive damage on the outer strands

suggests something has been rubbing against the cable.

Bancharel: It looks like 50% worn down over time.

When we looked at this cable under the microscope,

we were able to see that every external strand

showed these signs of wear,

which added up to very substantial damage.

Narrator: The pitch-up cable runs

from the control column in the cockpit to the elevator,

passing through a series of plastic guides.

Every time the pilot pulls the nose up,

the cable rubs against the guides.

Planes experience the most wear and tear

during takeoff and landing.

It's important for mechanics to monitor the number of flights

to help assess wear.

Bouillard: 48...

Narrator: Airline records provide a troubling clue.

Bouillard: More than 50 flights here.

Controller: Air Moorea, you are clear for final.

Narrator: Air Moorea planes make frequent short hops

and make many more takeoffs and landings

than most large airliners.

Limore: On average, it performed 50 to 70 takeoffs a day,

and landings, too-- the same plane.

Narrator: Investigators need to know

how all that back and forth movement

could have affected the pitch-up cable.

They devise a test that replicates

the friction on the cable.

But there's another factor that must be taken into account.

Bouillard: This is the only plane in the Air Moorea fleet

with stainless steel cables.

Desjardin: And we found out that there was a different type

of control cable used for this particular aircraft.

Narrator: The accident plane is a new addition

to the Air Moorea fleet.

The airline's other planes have control cables

made of carbon steel,

but flight 1121's cables are made of stainless steel.

Stainless steel withstands salt corrosion

better than carbon steel.

Desjardin: It would make sense to make the decision

to use stainless steel, so that your cables would corrode less

in a very saline environment.

Cables could be susceptible to corrosion more

than if you would operate over land.

Narrator: But stainless steel cables also have a disadvantage.

They wear down more quickly from friction--

something Air Moorea failed to take into account

when drawing up the maintenance schedule

for the twin otter that crashed.

Bancharel: A stainless steel cable contains chrome,

which makes it better at resisting corrosion.

It also contains nickel,

which can make it more sensitive to wear.

Narrator: Lab results confirm that the frequent short flights

helped wear away the outside of the stainless steel cable.

Bancharel: The stainless steel is worn, just like on Air Moorea.

The wear was the result

of rubbing against parts of the plane.

Narrator: It could be a crucial discovery--

one that finally explains why

a critical control cable broke in flight.

Investigators suspect friction weakened the cable

on the twin otter so much that it snapped

as the pilot was pulling his elevator up to climb.

Bancharel: At first we first thought that the cable broke

because of the wear.

That was our first impression,

because the wear was significant.

Narrator: Bancharel puts the theory to the test.

She recreates the force used by santurenne

to pull up the nose of the plane.

If she's right, the worn cable should snap.

But it doesn't break.

Bancharel: Once we performed this test,

we saw that with 50% wear, you still needed much more force,

a force ten times stronger than what you'd find in flight

during this phase of flap retraction.

Bouillard: Thanks to the tests,

we realized that even a cable worn down by 50%

could have withstood the stress of the entire flight.

Cable remained intact.

We had to figure out what phenomenon

could weaken the cable.

Something else helped to snap that cable.

What?

Narrator: Investigators know that planes sometimes sustain

hard-to-detect damage from small impacts with ground vehicles.

If an airport vehicle accidentally ran into the plane's elevator,

the impact may have broken more wires

in the already worn pitch-up cable.

Bouillard checks the records at both airports

on the twin otter's route--

Moorea and the larger airport in Tahiti where it parks overnight.

Bouillard: Thank you.

Narrator: He needs to know if the plane was ever involved

in an accident.

Bouillard: Nothing.

No impact reported.

We didn't find any evidence of impact on the control surfaces,

which eliminated the possibility of contact with another vehicle

during overnight parking.

Narrator: It's another dead end.

There seems to be no way to explain

why a cable would snap in flight--

until Bouillard notices something on the taxiway

at the busy Tahiti airport.

Bouillard: Tell me, how close do those jets get

to the Air Moorea planes?

We targeted the phenomenon of the exhaust from a jet engine,

a phenomenon called jet blast.

Narrator: Jet blast is the powerful exhaust

expelled from jet engines.

The hurricane force winds can reach speeds

of over 100 miles per hour.

Limore: A plane at full power,

a plane like an Airbus or like a Boeing,

whose power can flip a plane a few dozen feet behind it,

it's a phenomenal force.

Narrator: Investigators study the layout of Tahiti's Airport.

They need to know if the Air Moorea planes

could have been damaged by jet blast.

Bouillard: Ok.

The Air Moorea twin otters are parked here.

Narrator: They learn that Air Moorea parks its planes

very close to a taxiway used by powerful jets.

Airports routinely set up jet blast barriers

to protect planes from the dangerous force.

There should be barriers to protect the twin otters

at Tahiti's Airport, but they've been removed.

Bouillard: Now look at this.

Narrator: It's an important discovery.

Bouillard: The jets, they back out here.

These barriers were removed

to make it easier to go from one parking lot to another.

There was no longer this physical barrier

to protect the twin otter planes.

Limore: The Airbus or Boeing jets were found,

let's say, about 50 meters away from Air Moorea's parking--

very close.

Bouillard: The Air Moorea planes are parked

right in the path of the jet blast.

This plane had been parked in an area

that was prone to receiving blasts

from the large carriers during their departure.

We therefore arrived at this hypothesis--

that there was a very high probability

that the cable was weakened by jet blast.

Narrator: Alain Bouillard learns that Air Moorea's planes

are especially vulnerable to jet blast

because of an airline policy designed to prevent accidents.

The twin otters are parked with the elevators locked

in a nose-down position.

It makes it impossible to get off the ground

with the elevators locked.

Limore: It was locked by a device

that stopped the cables from moving

and prevented the elevator from moving.

Narrator: But the nose-down position likely increased

the damaging effects of the jet blast.

Investigators suspect that, like a sail in the wind,

the tilted elevators caught the full force of the blast,

putting extra strain on the locked pitch-up cable.

Bancharel: If the controls are locked,

it pulls and transfers this energy directly to the cable.

Narrator: They now wonder if the force of the jet blast

is enough to damage a worn cable even further.

Another cable test provides the answer.

Bouillard: There was a cable worn down by 50%--

a cable that was still able to resist a hefty amount of strain.

And then a jet blast phenomenon left the cable so fragile

that it only had one or two strands left intact.

Narrator: Rather than tearing the cable completely apart,

the jet blast left a few strands of wire--

just enough for flight 1121 to take off,

but not enough to survive the rigors of a seven-minute flight.

Bancharel: They were hanging by a thread.

Narrator: If the jet blast had severed the cable completely,

Captain Santurenne would not have been able

to get his plane off the ground.

But once Airborne,

Captain Santurenne and his 19 passengers

are one thin strand of wire away from disaster.

Investigators reproduce the forces created

as the pilot adjusts his controls.

Captain santurenne reaches 400 feet and retracts his flaps,

causing his twin otter to pitch down slightly.

He adjusts his elevator to pitch back up.

It's enough to snap the final strand

of the worn and damaged cable.

Bancharel: He didn't have a chance.

Bouillard: We determined that the force needed

to correct the pitch of the plane

was strong enough to break the last strand.

Narrator: There was nothing the pilot could have done

to save his plane and his 19 passengers.

Limore: You can imagine his reaction--what's going on?

The cable broke, the control column came back,

and by the time you analyze what happened,

the plane drops very quickly,

and a few seconds later you hit the earth.

Narrator: The Air Moorea accident killed 20 people

and forever changed the lives of the victims' families.

Bouillard and his team leave French Polynesia

determined to make it safer to fly on twin otters.

Bouillard: The first recommendation

was an urgent request to check the cables

on all planes equipped with stainless steel cables.

Narrator: Today there are tougher maintenance

and inspection standards around the world

for stainless steel control cables.

Desjardin: The main lesson from this investigation,

yes, is the risk of jet blasts at airports.

Narrator: The Air Moorea disaster

raised awareness throughout the industry

of the vital safety role played by jet blast barriers--

especially at airports that handle both large jets

and small commuter planes.

Eric Limore hopes it will be enough

to stop such an accident from happening again.

Limore: I dare to hope.

If not, what purpose did this accident serve?

To have 19 passengers die and have the same thing happen again

without learning anything?

It would be a shame.