Original subtitles

NARRATOR: It's the greatest aviation mystery of all time.

PILOT: Malaysia 370 contact Ho Chi Minh on 120.9 Good night.

NARRATOR: How can a Boeing 777 with 239 people on board

simply vanish without a trace?

The answer lies somewhere at the bottom of the Indian Ocean.

Imagine if we could empty the oceans, letting the water drain away to reveal the secrets

of the sea floor.

Now we can.

Using the latest underwater scanning technology, piercing the deep oceans,

and turning accurate data into 3D images.

key mysteries of Malaysia Airlines 370.

What lessons lie amid the wreck of previous air disasters?

Can Cold War technology extract vital clues from the deep ocean

And if the plane is found, what secrets could lie hidden in the tangled wreckage?

March the 8th 2014, Malaysia Airlines flight 370 departs Kuala Lumpur,

on a six-hour flight to Beijing

NARRATOR: As the Boeing 777 enters Vietnamese airspace

it suddenly drops off air traffic control radar.

A modern commercial airliner, carrying 239 people, has just vanished.

There's no mayday call and no wreckage at the point of last radar contact.

Aviation authorities struggle to understand.

REPRESENTATIVE: We believe family members should prepare themselves for the worst.

[crying]

NARRATOR: Families left behind demand answers.

WOMAN: [Speaking in Mandarin]

NARRATOR: The Malaysian government launches an investigation.

It will be the largest and most expensive in aviation history.

With multiple dead ends, false leads, a deluge of speculation,

but only a handful of real clues.

One of the first comes from the Malaysian military.

Powerful defence radar has detected the plane, turning back across Malaysia,

heading northwest up the Strait of Malacca, then disappearing out of range here,

just north of Sumatra.

It's a shocking discovery.

After it disappeared from civilian radar, it didn't crash

It continued flying.

JOHN: Initially when the airplane made a turn without talking to air traffic control,

in my mind, all bets were off.

It could be a terrorist event. It could be a deliberate act by a crew member,

it could be a mass failure in the electrical system.

NARRATOR: The next clue comes from space.

Although lost to radar, MH 370 continued to exchange what are called 'heartbeat' signals

with an Inmarsat satellite above the Indian Ocean.

The heartbeats come once an hour.

Frequency changes in the signals help experts calculate its direction of travel

and reveal something extraordinary.

After its initial track to the northwest, MH370 turned south and flew for six more hours.

From the travel time of each signal investigators also calculate the plane's distance

from the satellite.

These lines are called arcs.

Using the fuel load and cruisin speed, they can recreate a rang of possible flight paths

as the plane crosses each arc.

The final, or seventh, arc is deep in the Indian Ocean.

There are no more heartbeat signals beyond this point.

PETER: The data was extraordinary in as much as you're trying to establish

an aircraft's position based on information that was never intended for that purpose.

NARRATOR: It's the biggest breakthrough so far

instantly shifting the search 3,000 miles south of the last military radar contact

taking it into the jurisdiction of the Australian government,

and accident investigator Peter Foley.

PETER: This is something extraordinary that was captured by Inmarsat at the time

the aircraft was in the air, which very few people knew about and which is absolutely key

to the search and working out where to look for that aircraft.

NARRATOR: They start looking here:

a swathe of ocean running seven hundred miles along the seventh arc.

They estimate that the plane could lie 140 miles either side,

the maximum glide range of a 777.

The seventh arc is over 1,500 miles from the nearest land.

It will take two days for Australian search vessels to get there.

Two powerful storms have swept through since MH 370 disappeare

making the job of spotting debris even harder.

22 aircraft and 19 surface vessels look for wreckage, and possibly even survivors.

PETER: When an aircraft enters the ocean with energy, you expect to see a potential oil slick;

you expect to see all sorts of objects, actually, which are buoyant,

which are released from the aircraft as debris.

NARRATOR: Surface debris is normally the first step to finding a missing aircraft,

but it's not a guarantee.

Before MH370, the largest and most expensive search in aviation history takes place

here, 8,000 miles away in the Atlantic Ocean

hunting for the wreck of Air France flight 447.

What lessons lie amid this tangled wreckage, for those searching for MH370?

On June the 1ST, 2009, Air France 447 leaves Rio de Janeiro, Brazil,

carrying 216 passengers and 12 crew to Paris.

Weather reports indicate severe thunderstorms along the flight path.

Three hours and 45 minutes into the flight, as the plane nears the equator,

its on-board computers send a burst of emergency warnings

then falls silent.

Olivier Ferrante is in charge of the French search team.

The warning signals are his first clue.

OLIVIER: Some maintenance messages, and an important position message,

which was very useful for our search.

NARRATOR: It is a deep and remote stretch of ocean, but th search team has every advantage

A known flight path.

An accurate final position.

And then, surface debris found within five days.

And yet, despite initial optimism, it takes two years, four expeditions,

and forty million dollars to find the plane.

OLIVIER: Yes I remember that moment when we found the wreckage.

I was very careful, because we've had false alerts before and then it turned out to be

geology or not what we were looking for.

NARRATOR: Why does it take so long?

Using the data meticulously collected by the search team, combined with the latest

visualisation technology, It is possible to drain the Atlantic Ocean

revealing the hostile world that faces every deep-water search effort.

Immense water pressure.

Freezing cold, total darkness, and hidden dangers everywhere.

Finally, at 12,800 feet

the shattered remains of Air France 447.

Engines, wheel assemblies, and other heavy items lie together

their twisted remains a testament to the force of the impact.

Smaller, lighter, objects stretch along more than a third of a mile of sea floor,

equivalent to ten New York city blocks.

And a critical realization: the seabed wreckage is nowhere near the surface wreckage.

It's almost 24 miles away.

Investigators have wasted years searching directly underneath the surface debris

not realizing that ocean currents have carried it far away from the crash site.

The long and frustrating search for the French aircraft carries a warning.

Even with debris and an accurate final position, when a plane goes into deep water,

it's very hard to find.

A sobering thought for the team searching for MH370.

OLIVIER: Air France was very difficult with our area of 17,000 square kilometres.

But it's nothing compared to the the surface that the search teams have to for MH370.

It's much more difficult.

NARRATOR: In the southern Indian Ocean, investigators loo for surface debris for over two weeks.

Even with the aid of satellites, they find nothing.

JOHN: One of the greatest initial mysteries and that has transcended the entire

period of time that we have been looking for this airplane, where is the debris?

NARRATOR: With no debris they need to find another way to narrow the search.

So they focus on MH370's 'black box' data recorders.

Each has an underwater locater beacon or ULB.

In water they emit an electronic 'ping' with a range of just over a mile.

Find the beacons and you find the plane.

But time is running out.

PETER: Battery life on the ULB's is only 30 days.

Although they do last longer they fade out.

NARRATOR: By the time specialist pinger locater technology reaches the search

zone, there are just three days of battery life left.

[music]

O'DELL: Steer 319. OFFICER: Steer 319.

NARRATOR: Investigators have only a few days to locate MH 370's black boxes,

before their locater batteries run out.

Faced with a vast search zone, they decide to focus on commonly used air routes.

PETER: It was thought that if the aircraft had been in distress and was trying to make

to complete a flight for example to Perth, there was some recognized air routes.

NARRATOR: Australian navy vessel Ocean Shield steams to the point where the air route

to Perth intersects the seventh arc.

The team looking for Air France 447 also used pinger locaters i an attempt to discover the cras site.

They begin listening for signals within days of the plane's disappearance.

OLIVIER: In most cases the pinger locaters work, and that was our assumption before

Air France 447.

NARRATOR: Ships scour the search area for forty days but hear nothing.

The hunters wonder: are the locater beacons lost, or destroyed?

Returning to the remarkable drained seascape of the Air France 447 wreckage reveals

the scale of the problem.

The sea floor here is 12,800 feet below the surface

deep in the mid-Atlantic ridge.

And here amid the wreckage, nestling in the remains of the tail plane, the black boxes,

one with its locater beacon still attached.

A search ship passed directly over here, but detected nothing

The metal wreckage may have blocked the signals, or they could have been damaged

by the sheer force of the impact.

OLIVIER: I think they were unfortunately damaged, at that stage.

NARRATOR: Investigators listening for the MH370 black boxes can only hope

they'll have better luck.

They monitor the ocean for fifteen days, using three ships equipped with sensitive

listening technology, and military aircraft launching sonar buoys.

They do detect some signals, but conclude it's just random interference.

It's another disappointment.

But at this low point there's a dramatic new lead.

A team from Curtin University in Western Australia runs a network of sensitive underwater

microphones called hydrophones positioned all around the Australian coast.

They're designed to monitor earthquakes, Antarctic ice and wildlife and, remarkably,

one of them has picked up an unusual noise

1 hour and 14 minutes after MH370's last communication with the Inmarsat satellite.

ALEC: When we looked at the data from that hydrophone we found one signal that looked

as though it had interesting characteristics.

NARRATOR: Is this the actual sound of MH370's final moments?

Alec Duncan's team look for other audio recordings,

so they can calculate a geographical fix.

ALEC: One hydrophone does tell you a certain amount about the source of the signal,

so you can tell whether it's a whale, you can tell whether it's a snapping shrimp,

you can tell whether it's just noise from the mooring, but you can't tell direction.

NARRATOR: Fortunately, other agencies are listening too,

[explosion sound]

for the sound of illegal nuclea tests

with technology that can accurately pinpoint the source.

Just of the coast of Cape Leeuwin in Western Australia the Comprehensive Nuclear Test

Ban Treaty Organisation runs a listening post specifically designed to detect and locate

illegal nuclear tests.

The station has three hydrophones set one and a quarter miles apart.

They can determine the direction of a sound to within half a degree

and calculate the distance to the source, over thousands of miles.

And astonishingly, this network has detected the exact noise heard by the team from Curtin University.

ALEC: The analysis of the data from Cape Leeuwin told us that that signal had come

from the northwest and gave us a fairly accurate bearing

along which the source of the signal must have been.

NARRATOR: It's a tantalizing clue

and the sound does come from th direction of the seventh arc.

But when the scientists crunch the numbers, the source of the sound is far to the northwest

so far beyond the current searc area that it's considered not worth further investigation.

ALEC: Our conclusion was that he signal was most likely to be of geological origin,

such as a small under sea earthquake but we can't completely rule out

the possibility that it came from something to do with the aircraft.

NARRATOR: Faced with a new disappointment, the search team moves to a different approach:

searching the sea floor itself, using towed sleds carrying sonar scanners.

It will be the largest undersea hunt in history.

But before it can even start there's a new problem.

This part of the Indian Ocean has never been surveyed in detail.

The sleds will be close to the sea floor and no one knows exactly what is down there.

PETER: We knew we'd be operating vehicles very close to the sea floor,

which necessitated knowledge of what was down there and

so that we could avoid collisions with terrain.

NARRATOR: The MH370 team need a simple way to create a snapshot of the sea floor across the vas search area.

They find help in an unexpected place.

[music]

The team hunting MH370 across 463,000 square miles of Indian Ocean, face one big problem.

WALTER: More than 99 percent of the sea floor area in this region has not been covered by

ships with modern equipment, satellite navigation, multibeam echo sounding.

NARRATOR: Geophysicist Walter Smith thinks he might be able to fill in the blanks,

using satellites.

WALTER: The satellites actually cannot see the bottom, they're not seeing the ocean floor,

what they're doing is using radar to measure variations in the sea surface height.

NARRATOR: It's possible, thanks to gravity.

Mountains on the sea floor create their own gravitational attraction.

Surrounding water is drawn towards the mass, creating measurable changes on the surface.

WALTER: The smallest ones I can resolve are a kilometre or less in height and they move the sea

surface about 5 centimetres and the satellite has no problem resolving that.

NARRATOR: It doesn't have the resolution to spot the wreckage of an aircraft,

but it's enough to help create a basic map of the sea floor and identify hazards in the MH370 search zone.

What does the data reveal?

Using the exact information gathered by Walter Smith's team it's possible to drain away

the Indian Ocean to show what the ocean floor actually looks like.

As the water flows away it exposes a world no human has ever seen before.

Dramatic cliffs, more than twice the height of the Empire State Building.

Fault lines plunging almost 20,000 feet deeper than any canyon on land.

A volcano-dotted valley running for a hundred miles.

Operating underwater scanning vehicles in this terrain will take a huge amount of skill

and luck.

Armed with their new map of the sea floor, the search team deploys the latest in subsea technology.

Travelling deep underwater, these towed sleds begin to scan the sea floor.

And they will be guided by a game-changing new clue.

It comes from further detailed analysis of the final Inmarsat signal from MH370.

Engineers crunch the numbers, and discover something shocking

In its final moments, the plane descends rapidly, almost certainly because after

seven and a half hours in the air, it's run out of fuel.

Boeing engineers then simulate what happens when a triple seve exhausts its fuel

making it possible for the firs time to recreate the likely final minutes of MH370's mysterious flight.

The right engine flames out first.

The autopilot compensates for the imbalance with a hard left turn.

Minutes later the second engine flames out.

With no power, the autopilot switches off, leaving MH370 in a long spiral decent.

[crashing sound]

In every Boeing simulation, the crash site lies within 29 miles of the seventh arc.

These dramatic new insights immediately reduce the size of the search area,

from 463,000 square miles to just 23,000.

But that's still three and a half times the size of the search area for Air France 447.

ANDY: This is a massive search area.

It's magnitudes larger than any previous search I have ever worked on.

NARRATOR: Deep sea salvage expert, Andy Sherrell analyses all the data

that's being gathered underwater.

ANDY: Oddly enough when I first heard about MH370's disappearance,

my wife was in labour with our first child.

The news came on about the disappearance of the flight and my wife looked at me and she said,

'well that's a job you are not going to be involved with.'

NARRATOR: Andy has been involved ever since.

Using his knowledge from six previous investigations,

including a search for Amelia Earhart's Lockheed Electra.

As soon as the underwater scanning begins, it identifies shapes that could be manmade.

ANDY: So when you are reviewing the side scan sonar it comes down in a waterfall display

and you can see the different intensities of, you know soft sand versus hard rock.

NARRATOR: Guided by the scans, the team investigate 80 locations in detail

but find no trace of MH370.

Then in May 2015, the sonar picks up something new and exciting.

ANDY: It was a typical looking debris field that definitely warranted more investigation.

NARRATOR: The debris field covers an area similar in size to the wreckage of Air France 447.

Could this finally be the remains of MH370?

PETER: Sonar paints a very good picture of the sea floor,

and what you've got there but it's not perfect. It's not good enough to say with certainty

that a certain item might be an aircraft debris field.

You actually have to investigate with visual means.

NARRATOR: They launch an autonomous underwater vehicle,

armed with state of the art sensors, to take a closer look.

Using the actual data it recorded that day, it's now possible to drain away the wate

from over the site, revealing the most hopeful discovery so far in the hunt for MH370.

At one end a pile of chains.

Then a 23 foot long metal box

rusted machinery and finally three metal anchors.

They've found a shipwreck, its wooden hull long rotted away.

The site strewn with coal, probably cargo, on its final voyage.

They haven't found MH370, but in these dark uncharted depths they're casting light on

tragedies from a different age.

The investigators discover three other wrecks

Including this iron hulled sailing ship upright on the seabed.

And a modern fishing trawler, nets stretched out across the sea floor

proving that their technology can locate and retrieve objects as small as a piece of coal.

After fifteen months of detaile scanning, covering 23,000 square miles of sea floor,

there's still no sign of the missing plane.

ANDY: We have a very high confidence that we would have detected the plane in that search area.

So all of these factors gives us really high confidence that the airplane debris field is not in that area.

NARRATOR: The investigation continues, still guided by just two key pieces of evidence:

the Inmarsat calculations and Boeing's flight performance data.

Then, suddenly, a third line of inquiry brings hope of a breakthrough.

On a remote island on the other side of the Indian Ocean, 3,000 miles

from the search area, a piece of metal washes up on a beach

and it looks like it comes from an aircraft.

[music]

NARRATOR: In July 2015, a council worker on Reunion Island,

a French territory in the Indian Ocean, stumbles upon an unusual object on a beach.

It's called a flaperon.

There is one on each wing of a Boeing triple seven part of the mechanism that makes it rise or fall.

Boeing quickly confirms that its serial number matches that of the missing plane.

It's the first piece of physical evidence that MH370 ended its flight in the ocean.

OFFICER: It is my hope that this confirmation will at least bring certainty to the families

and loved ones.

NARRATOR: The suffering of the families attracts the attention of amateur wreck hunter

Blaine Gibson and sets him off on a remarkable personal quest.

BLAINE: I was very, very touched, very moved and realized that I needed to go do

what I could to solve this and what I learned, what that niche was,

was that there was no official search for debris that washed ashore.

NARRATOR: Blaine consults ocean drift experts, who direct him to Mozambique

where he makes an immediate discovery.

BLAINE: It was a triangular grey shaped piece of debris that said 'no step' on it.

Clearly aircraft.

I felt an enormous sense of responsibility because I realised that I had just found

the second piece of debris in the greatest aviation mystery in history.

NARRATOR: Boeing confirms that the "no step" debris is from MH370.

Blaine has found it 4,350 miles away from the main search zone.

Still acting alone, he continues to search.

BLAINE: We just found on Raike Beach this piece of debris.

We have not picked it up yet.

NARRATOR: Almost thirty pieces of debris thought to come from MH370 are recovered.

All on the western side of the Indian Ocean.

Blaine Gibson finds fifteen of them.

One piece stands out from the rest.

BLAINE: The most significant to me, and also to the investigation,

was the case around the TV screen on the back of the seat in front of you.

This is the one that brought tears to my eyes.

This is perhaps the last thing that somebody saw.

This is what anyone who flies on a plane would recognize.

NARRATOR: Debris like this, fro inside the passenger cabin,

confirms that MH370 hit the water hard.

PETER: Some of the items indicates that there was quite a large amount of energy

at the time the aircraft entered the water.

NARRATOR: Another piece of debris helps resolve a key question.

Investigators already believe the plane ran out of fuel.

But as it fell towards the ocean, was someone trying to save it with a controlled ditch

PETER: This section of main flap was found in Tanzania, Pemba Island in 2016 and

when imagery was passed to us we realized it was pretty significant.

NARRATOR: The flap extends on an internal support track.

Investigators discover that the track has left impact marks inside the flap.

That can only happen if it is in a retracted position strong evidence that the plane was

in its normal cruising state as it fell towards the sea.

PETER: It's been the subject of a lot of debate.

The hard physical evidence and our analysis showed that it wasn't a controlled ditch,

or there wasn't active control from the cockpit extending the flaps at the time

the flaps separated from the aircraft.

NARRATOR: The flap supports the theory that the plane ran out of fuel and suggests that

no one at that point was trying to ditch or save it.

But the debris doesn't only confirm how MH370 crashed.

It opens up a new and exciting line of enquiry that could narrow the search area.

DAVID: I think it's enormously important to find the plane,

because while planes crash routinely,

they don't just disappear and I think this terrifies people.

NARRATOR: Oceanographer David Griffin believes that the very first piece of debris recovered

the flaperon on Reunion Island, may be the key.

SKIPPER: This'd be a good spot, I reckon.

The wind's probably a bit stronger, I guess. Yep.

DAVID: This is a Boeing 777 flaperon off another aircraft, not MH370.

SKIPPER: We use this anchor to sink it again, alright?

NARRATOR: David Griffin is trying to recreate the journey of the flaperon across the ocean,

in the hope this will pinpoint the crash site.

He compares the flaperon's movement to these buoys.

Known as ocean drifters, they'r used daily all around the world to monitor ocean currents.

DAVID: We very quickly determined that these replica flaperons moved about

10 centimetres per second faster downwind than an oceanographic drifter.

NARRATOR: That may not sound like much, but when he compares it to known data about

the currents in the seventh arc on the day of the crash it help him estimate the flaperon's

travels during the 500 days it was afloat.

It's an extraordinary discovery

To narrow the search zone even, further David Griffin investigates

another strange feature of the debris.

DAVID: In addition to knowing where things are found in Africa,

the other key thing is where things have not been found and that's Australia.

NARRATOR: Why has no debris been washed ashore in Australia

Some of the ocean currents in the search area flow east towards the country.

A plane crashing here should leave evidence on Australian beaches.

DAVID: So this immediately tells us that all those potential parts

of the seventh arc, where the flow is strongly towards Australia,

they're essentially ruled out.

NARRATOR: When David Griffin looks at the historic drifter data from the day MH370

disappeared he finds three places on the seventh arc where the current would have pushed

debris away from Australia towards Africa.

DAVID: Here around 35, you have this area where everything is moving to the west.

Again up at 31, everything's moving to the west.

NARRATOR: If the plane crashed in one of these areas, it would explain why debris was not foun

in Australia.

And critically, only one of these locations matches his calculation of the flaperon's journey.

DAVID: So that led us to propose that 35 south is the most likely area for the crash.

NARRATOR: 35 south is an area that was not checked during the initial surface debris search.

For investigators, it's an exciting new lead.

But it comes too late.

MINISTER: It is with some level of sadness, certainly with a great deal of frustration

and disappointment that I stand here and acknowledge that the search,

the underwater search area effort, has been suspended.

NARRATOR: On January the 17th 2017, after almost three frustrating years,

the search for MH 370 is called off.

ANDY: Obviously I had strong feelings and am disappointed that we didn't find he aircraft

but it's not for the technical abilities or the giving it full effort and feeling good about

the job that we did at the time.

PETER: It was record breaking in terms of the time it took and the area that was covered.

There's never been a search as big by an order of magnitude.

NARRATOR: But will David Griffin's flaperon experiment persuade authorities

to search 35 degrees south?

It takes almost a year to answer that question, and new evidence from the skies.

[music]

Oceanographer David Griffin has a new theory.

He thinks MH370 is in an area called 35 south.

And in 2017, he finds more evidence pointing to the same place.

DAVID: I remember the day when I first saw those images in high resolution and I thought my God,

this, this really helps.

NARRATOR: Fifteen days after MH 370 disappeared, a French military satellite captured

images of possible manmade debris in the vicinity of 35 south.

At that time, the location wasn't considered a high priority area.

But, four years later, it's a different story.

DAVID: And I thought that this is really exciting.

This could be used to restart the search.

NARRATOR: A new year brings new hope.

In January 2018, salvage compan Ocean Infinity sets out on a brand new, privately funded, mission.

The seventh arc is still the focus.

But they expand the width of th previous search zone and move towards the new area

identified by David Griffin.

Once again, Andy Sherrell is on board and this time he has eight autonomous underwater vehicles or AUVs.

ANDY: One deep towed vessel would do a swing of about thirt days on site and over those

thirty days on sight they would cover about 35 hundred square kilometres.

Using eight AUVs simultaneously we can cover that in about three to four days.

NARRATOR: It's a high stakes gamble.

If they find nothing, they don't get paid.

Ocean Infinity searches the new priority area at 35 south.

In five months they cover an area almost equal in size to the original sea floor search.

But frustratingly, they find no trace of MH370.

The two search efforts have covered almost 92,000 square miles of sea floor

fourteen times the size of the Air France 447 search zone.

[music]

In May 2018 the Malaysian government announces that it will not support any new searches.

OFFICIAL: We cannot keep on searching for this 370 forever.

NARRATOR: Is the wreckage of MH370 waiting to be discovered

in the 386, 000 square miles of seventh arc search zone that remains unexplored?

Do clues to the mystery lie a few feet outside the circle of light and knowledge already cas

by the search teams?

Only time, money and the continued desire for answers separate us from the moment of discovery.

But the knowledge, hard won over two search efforts and four years,

will be invaluable for any future hunt.

Using the extraordinary data gathered by hundreds of investigators,

we can drain the area around th seventh arc to reveal what MH37 might look like

when it is found.

The debris will stretch out over thousands of yards.

The engines will be in one piece, the fuselage in thousands.

The nearby black boxes will reveal if anyone was in the cockpit at the end.

Emergency oxygen cylinders may show if the plane depressurized in flight,

whether intentionally or the result of an accident.

And personal electronic devices could reveal the experiences an fate of individual passengers and crew.

It will be a profound moment, one that Andy Sherrell has experienced before.

ANDY: It's a really surreal, kind of sombre moment because you realise all of a sudden

that you have found this you, gravesite, this place where all these people perished.

It's sad but it's also a bit of relief because you know that from that point forward

some answers are going to come back.

OLIVIER: I think you have to be to remain optimistic, and if you don't search,

you don't find.

So hopefully at the end you will find it.