All language subtitles for Mayday.S07E05.Sight.Unseen.1080p.AMZN.WEB-DL.DD+2.0.H.264-playWEB_track3_[eng]

Outside one of
India's busiest airports,

the early evening sky
ignites into a fireball.

This cloud just lit up,

it felt like you could
feel the heat.

Flaming wreckage
falls from the sky.

It's a horrifying crash.

I realized that the clumps
that I saw all around were

either the remnants
of the aircraft,
or dead bodies.

When investigators arrive,

they find the twisted remains
of two passenger jets.

Three hundred
and forty-nine people are dead.

Vital clues are buried
deep underground.

Investigators must
piece together
the day's events.

Saudi 763 will maintain 140.

Kazakh 1907 now reach 150.

How had two crews
that should have known

each other's positions...

ended up in the worlds
deadliest mid-air collision.

Mayday! Mayday!

Indira Gandhi
International Airport,
New Delhi.

A Gateway to India.

November the 12th, 1996.

Busy?

Air Traffic Controller
VK Dutta arrives

for the late afternoon shift.

There was one
supervisory officer.

There was one person
who was sitting beside me

and he was assisting me.

And... the things
were all normal.

But normal
at Indira Gandhi
doesn't mean calm.

This is becoming
one of the most

congested airports
in the world.

In 1990, the Government
of India signed

open skies agreements with
several different countries.

Those pacts have
made it easier

for foreign airlines to land
at Indian airports.

Many airlines are taking
advantage of the new policy.

Air traffic controllers
are now handling more
traffic than ever.

The open skies
policy acted as a catalyst
in the air traffic growth.

The volume of traffic
grew from, I believe,
175 movements a day

to around
225 movements a day.

We have to perform...

we have to perform,
uh, during that time.

So whether 10 aircraft
come on that time,
or 20 comes,

so, you have to handle them.

Just past six o'clock,

Saudi Arabian Airlines
Flight 763 takes off
into the sunset.

Gear up.

Gear up.

Clear on left.

Captain Khalid Al-Shubaily

powers the Boeing 747
away from the runway.

His Co-Pilot Nazir Khan
handles all radio
communication.

There are 289 passengers
on board.

Many are Indian workers
returning to their jobs
in the Middle East.

Saudi 763.
Airborne 03,

contact radar
127 decimal 9.

While Flight 763
was on the runway,

its movements were
tracked and directed

by an Air Traffic Controller
in the airport's tower.

279. Good day.

But shortly after
the plane takes off,

the Tower passes
the pilots over to

Approach Controller
VK Dutta,

who's in another room
at the airport.

Approach Controllers
at Indira Gandhi

guide planes through
the airspace beyond
the runways.

They're in charge of all
arriving and departing flights
within 110 kilometers.

The Approach
Controller normally

is responsible for arrival
and departures of the aircraft

which are coming in.

They are safely
and expeditiously, you know,

they are brought
to the final approach.

Tonight,
Dutta is controlling
five flights.

Some of these are leaving
the airport,

while others are coming in.

His task is to keep those
planes spaced safely apart,

but not so far apart
as to cause any delays.

There is continuous
coordination with the tower

who handles the ground traffic.

So he would tell
approach controller

that this fellow is ready,
and, you know, uh...

he is to be accommodated
between these two flights.

So that kind of dynamics
we do...

we were doing at that time.

Saudi 763, approaching flight
level 100.

Roger, climb flight level
140.

Clear to climb 140,
Saudi 763.

This evening,
a United States Air Force
cargo plane

is coming in
for a landing.

Even though
it's an Air Force jet,

this flight
is Dutta's responsibility.

I think we probably
had three or four

back and forths
with the controller,

where he was verifying
our altitude,

or checking on our altitude,

telling us about other
traffic in the vicinity.

Saudi 763,
approaching 1-4-0 for higher.

Saudi Flight 763
reaches its last assigned
altitude of 14,000 feet.

The pilots request permission
to fly higher.

Roger, maintain
flight level 140.

Stand-by for higher.

In order to coordinate
incoming and outgoing traffic,

Dutta wants the Saudi flight
to stop climbing.

Saudi 763 will maintain 140.

Dutta is concerned
with another plane,

now flying east for a landing
at Indira Gandhi Airport.

It's a passenger jet operated
by Kazakhstan Airlines.

The Ilyushin-76
is a massive Russian plane.

Originally built
for the military,

a modified version
is now widely used
as a commercial airliner.

Dutta wants it to pass over
top of the Saudi flight
before landing.

before landing.

After that,
he'll let the Saudis
continue their climb.

They were supposed to cross,

uh, maintaining
a 1000 feet of separation.

Kazakh 1907,
now reaching 150.

46 miles from
Delta Papa November.

Roger, maintain
flight level 150.

Identified traffic
12 o'clock reciprocal,
Saudi Boeing 747.

Dutta doesn't want
the Kazakh flight to be
surprised to see the Saudi jet.

Since planes don't have radar
to track other aircraft,

they rely on controllers
to warn them about
other planes nearby.

Maintaining 150,

Kazakh 1907. Will report.

How many miles?

All pilots tuned
to the approach control

radio frequency are able
to hear one another

as they communicate
with the ground.

How many miles?

Eight miles now.

It was strictly visual,

and trying to, trying to pick up
on the radios

where everyone else is at,
and what they're up to.

Traffic is at eight miles
level 140.

Suddenly,
a massive explosion shatters
the evening's calm.

All at once,
out of the right side
of the window,

right side of the cockpit,
um, this cloud just lit up.

Are those missiles?

To my mind's eye
they were missiles

kind of cork screwing
picking up speed was
what they looked like.

And they looked like
they were coming right at us.

We actually started
veering the aircraft away

before it became apparent that
they weren't coming at us.

The Saudi Airlines jet
spirals towards the ground.

Delhi, this is 1815.

1815, say again.

Got on the radio right away
called the controller.

We saw something that
looks like a big explosion.

Then it struck me that
something has gone wrong.

On Dutta's radar screen,
both the Saudi jet

and the Kazakh plane
have simply vanished.

When I saw the blips
are coming,

and so I watched
the sweep again.

But they were
not there at all.

We then heard
the controller call for...

for the Saudi Air jet
and the Ilyushin.

Saudi 763?

With no response.

That was obviously
very bone chilling.

Something tragic
has happened in the skies
near New Delhi's airport.

VK Dutta is about to become
the target of an investigation

into one of the deadliest
plane crashes of all time.

Kazakh 1907,
report your position.

At New Delhi's airport,

a sense of dread
is growing.

Two planes have vanished
from Approach Control's radar.

The worst nightmare

an air traffic controller

has is the mid-air collision.

Saudi 763?

Together,
the two missing planes

were carrying 349 people.

Kazakh 1907, report position.

I gave one or two calls
to Kazakh and Saudi.

Saudi 763?

I forgot
how many kids I have,

where my wife is,
whom I'm related to.

US Air Force Pilot
Captain Tim Place

soon confirms the worst.

Delhi, this is 1815.

1815, what did you see?

Two distinct fires
on the ground.

Two fires on the ground.

Confirm?

Confirmed.

Confirmed.

Roger.

My senior came to me,

so I told him, uh...

an accident had happened.

I told our people who were
to do the search and rescue

that the aircraft
have crashed

at 40 nautical miles
west of Delhi.

Two planes have gone down
over Charkhi Dadri.

Charkhi Dadri
is a town 65 kilometres
west of New Delhi.

Its mustard and grain fields
are now burning

with the twisted wreckage
of two ruined airplanes.

All of a sudden, the sky
turned a bright red color,

and I saw fire and smoke.

One plane
started to come towards us.

There was fire
and parts of the plane
were flying everywhere.

People were running.
The plane's engine broke off

and the plane started
to spin out of control
and fell into the field.

I was told
that there's been
a mid-air collision.

Apparently there's a jumbo jet
which may be involved,

and why don't you
just head out?

There was this adrenaline rush
in that sense, I was...

I was very new
in the business,

and I knew I had to get
that story.

Vishnu Som
is assigned to report

on the crash
for New Delhi Television.

He arrives in the darkness
of night, a few hours
after the crash.

We parked our vehicle
on the side of the road,

and it was a...

I mean, there was
a fair bit of moonlight.

He and his cameraman

are one of the first
media crews
to arrive on the scene.

Turn off the light.

We don't want
to attract attention.

The police have likely
cordoned off the area.

I stepped onto the field,

and, I mean, I thought
it was a fallow field,

nothing was growing over there,
because it was just sand.

Um, and you know,
because it was dark

and our only visual reference
was, was the moonlight,

we just sort of kept going.

And then, I remember
seeing clumps around me.

You know, just these,
these little piles
on, on all sides.

And because there wasn't
enough light, I didn't know
what exactly it was.

And then I stopped,
because I said, you know,

something's terribly
wrong over here.

Turn on your lights.

Turn on your light.

I realized that the clumps
that I saw all around me were

either the remnants
of the aircraft,
or dead bodies.

There was a tree
just maybe

fifteen feet away
from me to my right.

There was this burnt corpse
on that tree,

and that's an image which,
which, you know, comes back

and continues to haunt me
even after so many years.

As night turns to day,

hope of finding
any survivors fades.

None of the passengers aboard
either plane has survived.

Three hundred and forty-nine
people are dead.

It's the worst mid-air
collision of all time.

News of the crash spreads
around the world.

What remains clear is that
there was more than

one set of factors that might
have resulted in the collision.

We have two
very separate wreckage fields.

Captain KPS Nair

is one of the first
investigators on the scene.

I was aghast,

horrified.

I can't explain it, because
I had never seen anything
like that before.

It is something...

which I can't explain.

The Kazakh flight
and the Saudi Airlines jet

have fallen seven kilometres
from each other.

Investigators have two
separate crash sites
to examine.

But they know one cause
will explain both accidents.

It's unlike a single
aircraft falling somewhere.

Two large body aircraft

colliding with each other

in the sky...
There are different causes.

How had two planes
that were supposed to be
1,000 feet apart collided?

Investigators consider
three possibilities.

An error on the part
of the air traffic controller,

an error by
one of the crews,

or the failure
of an instrument
on one of the planes.

They hope the mangled wreckage
will hold the clues they need.

Their first priority
is to find the black boxes
from both planes.

They record
cockpit conversations

along with critical data
about the flight,

like its altitude,
speed and heading.

Although fire has ravaged
the wreck sites,

the black boxes
from both planes

are found on the first day
of the investigation.

But for the moment,
they hold their secrets.

It will take several months
for experts to extract data
from the recorders.

In the meantime,
investigators focus
on conversations

between the two planes
and the air traffic controller.

In this particular case, we...

had the evidence
of the ATC transcript.

Without onboard radar,

the planes around
Delhi's airport

rely on air traffic controllers
to guide them.

VK Dutta comes under
enormous pressure.

Did he make mistakes
that caused the worst
mid-air collision ever?

Those times were bad.

These media people,
they cried foul.

So I told them that, you know,
there's no fault of mine.

Hi, I'm VK Dutta.

I'm sorry
to keep you waiting.

Have a seat.

Investigators want
to know everything

that Dutta did
on the night of the crash.

Was traffic heavy?

Evenings are always busy.

Dutta's radar doesn't track
a plane's altitude.

Instead, controllers
in New Delhi

write a plane's
last reported position
on a strip of paper.

The strips are
continually updated.

It's the only way
for controllers to keep track

of the altitude of the planes
under their control.

Level information
is not there.

So level has to be
confirmed by the pilot.

Kazakh 1907 now reaching 150.

Air traffic controllers can
only know a plane's altitude

when the pilots report it.

Are these your notes?

Yes, sir.
This is the Kazakh one,

and this is the Saudi one.

Investigators learn
that Dutta was in charge

of five flights at the time
of the accident.

And that the Saudi
and Kazakh flights were flying

in opposite directions
of the same aerial pathway.

The area that Dutta manages
is divided into a network
of air corridors.

Controllers use them
to channel flights in
and out of the airport.

But many of the corridors
are used for military flights.

In fact, even at such
a busy airport,

there's only one main corridor
for commercial planes.

In cases like this,
there are strict rules
he has to follow.

Between two aircraft
the requirements specify

a vertical minimum separation
of 1,000 feet.

When aircraft
fly through the sky,

they leave turbulence
in their wake, like boats
on the water.

It can affect the planes
around them.

Air Traffic Controllers
deal with this

by keeping planes
at different altitudes.

Roger, maintain
flight level 140.
Standby for higher.

Dutta was supposed
to ensure that the two planes

were 1,000 feet apart
as they approached
each other.

He planned to do
what he had done
many times before.

Have the incoming plane
pass 1,000 feet

over the top
of the outbound plane.

It was a routine procedure,
but somehow,

the two planes had ended up
on a collision course.

One of the two planes was not
where it should have been.

Investigators wonder
if Dutta made a mistake

that led
to the horrific crash.

Pouring through
the ATC transcripts,

investigators quickly learn
that Dutta had given

the two planes
the proper directions.

But since his radar
doesn't display altitude,

there was no way for him
to tell if the planes
followed those instructions.

Investigators are so convinced
that Dutta did nothing wrong

that three days
after the crash
he's back on duty.

When my family
and other people heard this,

there was a little
sigh of relief,

that, you know,
our guy is safe.

Investigators return
to the crash site.

They are hoping to recover
certain instruments
from the two aircraft.

Perhaps a mechanical
failure had led

one of the planes off course.

Normally, the altimeter would
have stopped at the point

where the accident
took place.

And we wanted to know
what altitude

they were registering
at the time of the accident.

But the Saudi cockpit has
plunged deep into the ground.

The accident investigation
becomes an excavation.

The Saudis' nose portion
was well below the earth.

It was about
10 to 12 meters,
um, below.

The end of the nose
had gone that far below.

Machines had to
be brought in.

Excavators to dig up and lift
the cockpit of the
Saudi aircraft.

The altimeters
of the Kazakh flight
are easier to find.

That plane didn't crash
nose first.

There's some chance
there are clues about

its exact altitude
at the time of the accident.

When they're pulled
from the wreckage,

investigators discover
that there is indeed

something strange
about the altimeters.

Both the captain
and the co-pilot

have an altimeter
in front of them.

But in this case,
they do not have
same reading.

There was a difference
between the two

by about 300 feet.

Strange.

Perhaps the conflicting altimeters

had led the crew off course.

But the difference
in readings

may simply have been caused
by the force of the crash.

At this point,
investigators don't know.

Mostly there, and there.

As close as you can get.

Investigators need to discover

which of the two planes
was at the wrong altitude.

They explore other evidence.

The pattern of the damage
on the two planes

may help answer
a critical question.

What was the relative angle
between the two aircraft

at the time of the...
their contact?

Most of the pieces
from the two planes
are kilometres apart.

But a large section
of the tail

from the Saudi aircraft
is found near the beginning
of the debris field.

This suggests it was
one of the first pieces
to come off that plane.

The significant
point of contact

in this particular accident
in the air, was between

the tail end of the IL-76,

and the wing portion of

the Boeing 747 of Saudi Air.

The tail of the Kazakh plane
appears to have pierced

through the left wing
of the Saudi jet.

If that's the case,
the Kazakh flight

hadn't been above
the Saudi jet
when they collided

as air traffic
controllers thought.

It must have been below it.

It's a puzzling discovery
that adds to the mystery.

Investigators still
don't know

which plane was
in the wrong airspace.

What they do know is that
once the two planes hit,

there was no hope
for either crew.

After hitting the other
plane's wing,

the Kazakh plane's tail
tore through

the horizontal stabilizer
at the rear of the Saudi 747.

Five-and-a-half meters of it
is torn off.

Without it, the Saudi crew
can't control their plane.

The result is,
the aircraft goes into
uncontrollable spiral.

And in this particular case,

I would say, both aircraft
had gone into that situation.

What they've
found in the wreckage
of the two jets

frustrates the investigators.

They now understand
how the planes collided,

but they still don't know
why they were
at the same altitude,

or in fact, what altitude
they collided at.

How had the Kazakh jet,
which was supposed to be
above the Saudi flight,

ended up below it?

Almost two weeks
after the accident,

Captain Ashok Verma joins
investigators at the scene.

By that time,
the operations for digging

the Saudi Air cockpit
had been completed.

Whatever equipment
was recoverable
had been recovered.

Like the rest of the evidence
uncovered so far,

the instruments from
the Saudi plane

don't help explain
what happened.

The force of the crash
has completely
destroyed them.

I can't find anything.
Too much damage.

I agree. Look at this.

We could hardly find
any useful material.

With the disappointing discovery,

the investigators are
forced to move on.

They've learned all they can
at the crash site.

The case now depends
on what they can find out
from the black boxes.

Investigators hope
that somewhere
on the cockpit recordings,

or buried in the flight data,
are the clues they need.

Where were the planes
when they collided?

And how had they ended up
on a deadly collision course.

Get to the 150,
because at the 140...

It's been
three months since

the mid-air collision
of two passenger jets
near New Delhi.

Investigators have been
frustrated by a lack
of conclusive evidence.

They hope the planes'
black boxes will help them
solve the case.

In order to avoid
any suggestion of bias,

the boxes from the Saudi flight
are being analyzed in England.

Technicians from
the Air Accidents
Investigation Branch

try to extract valuable data.

The neutrality of state
where the recorders are handled

was an essential thing.

Each plane was
equipped with two black boxes,

a flight data recorder,
and a cockpit voice recorder.

The flight data recorder
contains information

on dozens of aspects
of a plane's performance.

Among them, the altitude,
the airspeed,

and the changes pilots make
to the flight controls.

The cockpit voice recorder
picks up all the conversations
in the cockpit.

279, Good day.

As investigators
try to learn more about
the collision near New Delhi,

they use the information
stored on the black boxes

to make
a chronology of events.

Peter Sheppard is head
of the recorder section

of the Air Accidents
Investigation Branch.

He'll work backwards
from the moment of impact.

The point of the collision
is reasonably well defined

by rapid changes
in parameters on each,
each aircraft.

If we make that
our time zero point,

we can then relate that
to individual times,

and then build up, you know,
a common time base.

First,
Sheppard and his team
concentrate on the Saudi 747.

Saudi 763 approaching
140 for higher.

Roger, maintain
flight level 140.

Standby for higher.

Saudi 763,
will maintain 140.

The CVR reveals
that the Saudi pilots received

clear instructions
about their altitude,

and seem to have
understood them.

After being told to hold
at 14,000 feet,

there was no discussion
of climbing to
a higher altitude,

which would have
taken them into the path
of the Kazakh flight.

Next, Sheppard looks
at the flight data recorder

to confirm that
the Saudi flight actually

followed the instructions
it was given.

The recorder from
the Saudi flight told us that

the altitude had been normal
during climb out

The Saudi pilots
leveled off at 14,108 feet.

Well within
their safe corridor.

It had leveled
at its assigned altitude,

of, um, 14,000 feet,

and continued to fly level.

The Saudi pilots followed

the ATC instructions
meticulously,

which is borne out by
their confirmatory calls
back to the ATC.

Air traffic controllers wanted
the two planes separated

by 1,000 feet,

and wanted the Saudi plane
to fly below the Kazakh jet.

If the Saudi pilots
did nothing unusual,

suspicion is growing
that somehow,

it was the Kazakh plane
that was in the wrong place.

Alarmingly, when investigators
examine the information

from the Kazakh jet's
flight data recorder,

they discover that
it descended far below

the 15,000 feet
it was supposed to stay at.

Moments before the collision,

the Kazakh plane
is at 14,100 feet.

Almost 1,000 feet lower than
its assigned altitude,

and less than ten feet below
the Saudi flight.

It then powered directly
into the Saudi jet.

The Kazakh crew had not
stopped descending

at the altitude
they were cleared to.

That was 15,000 feet.

But why had
the Kazakh flight dropped
so badly off course?

Kazakh 1907, report position.

Kazakhstan Airlines
presents one theory

for their plane's
dramatic loss of altitude.

The Kazakhstan defense
mainly relied on presence
of turbulence.

Perhaps a sudden
burst of turbulence had
forced the plane lower.

The data recorder of
the Kazakh flight

does seem to indicate that
the crew had a bumpy ride.

It shows two distinct
and sudden drops
of more than 400 feet.

The airline claims
both of these drops were
caused by turbulence.

But Peter Sheppard
isn't so sure.

When we saw the jumps
of 250-500 feet,

our initial response was that
these can't be right.

I mean, you know,
it... it was...

the rate at which
they changed
was beyond that,

that an aircraft can
actually perform.

What else could cause
the plane to drop so quickly?

Or at least seem to drop
so quickly?

Sheppard searches
for an explanation.

We tried to resolve
the inaccuracies

in the Kazakh recording
by looking at the other

parameters that
were recorded

and trying
to derive altitude, um...

using these other recordings.

It's intricate math.
By using information

including the speed
and rate of descent from
the flight data recorder,

Sheppard determines that
the plane was on a steady
downward approach.

The reason for the apparent
sharp drops is simple.

Sheppard learns that
the sensor that sends
altitude information

to the flight data recorder
was faulty.

It would stick,
and temporarily stop
sending information.

When it got unstuck,
it would wrongly appear

as though the plane had
lost considerable altitude.

It's as if there was
bit of glue on one area
and it stuck in that.

And eventually...

the altitude changed so much

that the force
on it made it jump...

again and it stuck there
for a little while.

Investigators can now
conclusively dismiss

turbulence as a factor
in the collision.

So there's no sudden descent?

Scanning maintenance records,

investigators also discover
that there was no problem

with the Kazakh
plane's altimeters.

They conclude that
the difference found

in the cockpit instruments
was a result of the crash,

it didn't cause it.

To understand
why the Kazakh plane
kept descending

after it was told to hold,

investigators turn
to the cockpit voice recorder.

It begins long before
the crash itself.

Initially, there are no hints
that anything is wrong.

Kazakh 1907,
report level passing.

Passing 240,

Kazakh 1907.

Because the Ilyushin 76
is a modified military plane,

it has another
unusual feature.

A position
for a radio operator
in the cockpit.

Egor Repp mans that position,

and handles all communications
for the Kazakh flight.

Roger, over to Delhi
Approach 127 decimal 9.

127 decimal 9.
Bye bye, Kazakh 1907.

As the aircraft
nears the airport,

Repp gets in touch with
Approach Controller Dutta.

Delhi Approach.
Good Evening. Kazakh 1907,

passing 230 to 180.

I told Kazakh to descend,

and maintain
flight level 150,

that is 15,000 feet.

Roger Kazakh 1907,

descend flight level 150,
report reaching.

One thousand feet
vertical separation
is sufficient,

and that was granted
to the two aircraft.

Kazakh 1907
now reached 150.

The Kazakhstan
radio operator had...

at one time stated
reaching flight level 150.

It's just one minute
before the impact.

And at this point
the Kazakh plane appears

to be right where
it's supposed to be,

one thousand feet
higher than the Saudi plane.

But investigators know that
instead of levelling off,

the plane continued
to descend.

This is where
the trouble starts.

As investigators compare
the flight data information

to the cockpit voice,
they notice
something disturbing.

Kazakh 1907
now reached 150.

When Repp
calls out that they've
descended to 15,000 feet,

he's actually over
1,000 feet higher
than he thinks he is.

Investigators wonder
how he could make
such an enormous mistake.

Why would he say he was
at 15,000 feet

when in fact
he was at 16,000?

They consider the layout
of the cockpit.

A radio operator
does not have
his independent altimeter.

There are two metric
altimeters fitted in front of,

uh, one each in front
of the pilots,

with some effort

the radio operator
could also see this.

Whatever the reason,

Repp is mistaken about
his plane's height.

And he's the only one
in contact with the ground.

Despite being told to remain
at 15,000 feet,

the plane continues
to descend.

As it does,
Dutta issues a warning
to the Kazakh pilots.

Identified traffic
12 o'clock reciprocal,

Saudi Boeing 747
and ten miles.

Likely to cross
in another five miles.

Report if in sight.

He tells them to watch out
for the Saudi flight.

But the Kazakh jet just
keeps flying lower.

Ahead?

Ahead!

Just before the crash,
Egor Repp seems to have

recognized that the plane
is now flying dangerously low.

But his warning
doesn't come in time.

Keep the 150!
Do not descend!

Accelerate Sanya!

The cockpit voice recorder

proves what investigators
found in the flight data.

At the time of the crash,
the Kazakh jet was trying

desperately to get back
on course.

Get to the 150,

because on the 140...

But investigators
are still puzzled.

Why had the Kazakh plane
kept descending?

After ruling out,
uh, controller's error,

ruling out mechanical failure,

you have to go further into
the details of human behavior

during the operation
of a flight.

Kazakhstan is one of several
now independent republics

that used to be part
of the Soviet Union.

The national airline
has a reputation
at Indira Gandhi Airport.

There was always a sense
that, you know,

these were small fly by
night operators

essentially doing
the charter business,

and they didn't necessarily
follow the conventions

of modern Western aviation.

We examined the background
of their knowledge
of English language.

The crew
in the Soviet states...

uh, they passed
English examination,

but they're not fluent
in spoken English.

Verma now
listens more closely
to the cockpit voice recorder,

looking for an indication
that the crew misunderstood
their instructions.

Had a language barrier
caused the crash?

How many miles?

Traffic is at eight miles
level 140.

Did the Kazakh pilots
confuse their own altitude

with that allocated
to the Saudi aircraft?

Report eight miles.

Verma finds that
members of this crew

weren't communicating
clearly with each other.

Egor Repp was responsible
for communication
with the ground,

but there's no indication
that the pilot and co-pilot

were listening
to his instructions.

Switch on the engine
inlet heating.

While the rest
of the crew was busy
discussing arrival procedures,

Repp alone seemed to be
occupied with their altitude.

Now looking 1907.

It is a usual practice that...

the briefing for the arrival

is completed before
the start of descent...

so that all crew can pay
full attention to the radio.

While the radio operator
appears to have understood

that the Saudi plane was
at 14,000 feet,

investigators believe
the co-pilot thought that

he was cleared
to 14,000 feet,

and continued his descent.

Hold the level!

What level were we given?

When the pilot
does respond,
he seems confused.

I think, pilots did not pay
that much attention,

and relied too much
on the radio operator

to navigate the aircraft
during this critical phase.

The decision
to increase power

and stop descending
ends in tragedy.

Keep the 150!
Do not descend!

Accelerate Sanya!

Get to the 150,

because on the 140...

The final report
points a finger squarely

at the crew
of the Kazakh plane.

In the wrong place
at the wrong time,

a simple misunderstanding
led to the deaths
of 349 people.

The investigation concluded

that the primary cause
of this midair collision

was non-adherence
to the authorized altitude

allocated to
the Kazakhstan aircraft.

Investigators are confident
they know what caused

the worst mid-air collision
in aviation history.

But there are steps
they want the industry

to take to help make
Indira Gandhi airport safer.

What they find is that
the technology

that could have prevented
this accident was already
at the airport.

Saudi 763.

Investigators have
determined that poor
cockpit communication

and a simple misunderstanding
caused a devastating accident

which killed
almost 350 people.

But technology existed
that could have helped
avoid this accident,

systems that would have helped
both the pilots in the air,

and the controllers
on the ground.

Investigators are especially
critical of the radar

that was being used
in New Delhi.

Air traffic controllers
did rely

on fairly outdated
technology at that stage.

Um, there wasn't any
secondary radar available

at Delhi airport there was
only an old primary radar.

Primary radar
sends out radio signals

to locate airplanes
in the sky.

The signal bounces off
the plane and back
to a dish on the ground.

It reads a plane's position,
but not its altitude.

The primary radar
gives you 2D picture.

Secondary radar
works differently.

A transponder aboard
an aircraft sends a message

to the ground with
key information

about the flight,
including its altitude.

Saudi 763, approaching
flight level 1-0-0.

Roger. Climb to
flight level 140.

On the day of the collision,

Approach Controller VK Dutta
could only rely on

what the crews told him about
their aircraft's altitudes.

Kazakh 1907,
now reached 150.

The Kazakh Radio Operator said

that they were flying
at 15,000 feet.

But Dutta had
no way to confirm that.

If he had known
the Kazakh flight's
actual altitude,

he could have diverted
the Saudi flight
from its path.

That is the a 3D picture.

So you can, you have some,
some time to react to it.

You can take
the aircraft away.

At the time
of the accident,

India had ordered
a $118 million

air traffic control system
with secondary radar,

and more sophisticated
communications

and navigational equipment.

The system had originally
been scheduled to be installed

two weeks
before the accident.

But on the day of the crash,

the system hadn't even
been unpacked.

Secondary radar
is an advancement
on the primary radar.

And in this particular case,

also by getting
the altitude information

it could have been possible
that the accident

of this nature
could have been avoided.

In the year
following the accidents,

there would be
three near misses

near Indira Gandhi airport.

It would take more than
two years for the secondary
radar system to be installed.

Today, controllers
at Indira Gandhi
International Airport

see an airplane's
flight number,
altitude and heading.

It's far more information
than controller VK Dutta

had available to him
on the day of the accident.

Experts believe another
piece of technology

could have helped prevent
the collision, TCAS.

TCAS equipment generates
cautions and warnings
for the crew.

It allows them time to react,

draws their attention
to the situation around

and it, uh, looks into
vertical separation.

TCAS is a collision
avoidance system

that can be installed
on board airliners.

In many countries,
the technology is mandatory.

It alerts pilots when other
flights are coming too close.

The system also automatically
tells them what evasive action
they should take.

Neither plane was equipped
with TCAS.

The Indian Airports Authority
has also made the airport safer

by re-designing
the air corridors coming
and going from the runways.

At the time of the collision,
there was one main

air corridor for
commercial planes

landing and taking off
from Indira Gandhi
International Airport.

With the increase
in air traffic,

that single corridor
was becoming too crowded.

In the wake of the accident,

more air corridors were
opened for commercial flights.

In general, aviation safety
standards has improved.

The concern for the safety
has improved.

Out of date technology
and poor communication
led to this crash.

But like almost
every aviation accident,

it was a chain of seemingly
minor events

that ended in disaster.

In retrospect...

those were some
very unlucky people

to meet in the sky that night.

You know, it's a...
it's a one
in a million chance

for that to happen. Uh...

Certainly there were
other things that
could have helped.

Radar, uh, collision
avoidance systems...

And I... And I think
we continue to make
advances there.

I... I don't worry
about flying.

Um, certainly...
you know, destiny,

I don't know. It was...
glad we weren't
five minutes

in front of where we were
at, that's for sure.

VK Dutta
went on to have a long career
as an air traffic controller.

Today, he works at a college,
training young controllers.

So I'm chief instructor there,
so I'm training ATC's.

I'm addicted to my job.
I love it. I really love it.

Dutta, who was initially

suspected of having
caused the crash,

helped implement
the changes to make
New Delhi's airport safer.

His efforts have paid off.

The airport now handles
20 million passengers a year.

Since the new radar system
was installed,

and the new corridors opened,

there hasn't been a fatal
accident at this airport.