Original subtitles

A horrific collision in the skies above southern Germany is witnessed by people

on the ground.

71

people

are dead.

We as accident investigators did not have an idea of what exactly happened.

Doesn't make sense. The radar data only deepens the mystery.

Neither one is trying to get out of the way.

She's got to use the facilities.

Descend? Really? We're going to descend?

To solve the mystery, investigators will need to disentangle a web of critical

radio transmissions.

The controller is guiding us down.

A lot of things had to fall into place just the wrong way for this to occur.

It really woke a lot of people up.

It's 11 p.m. in Switzerland, and airports across the region are closing

down for the night.

You're off.

See you in a few hours.

In the Sky Guide Control Center in Zurich... Thai Inter 933, proceed to

Algoi. Copy. Proceed to Algoi. Thai Inter 933.

Air traffic controller Peter Nielsen is working the night shift.

He's been on the clock for just over three hours and has six more to go.

Tom Lawson is a former Sky Guide controller who worked with Peter

Nielsen.

The night shift in Zurich at the time had quite a lot of traffic.

But around 11.30, 12 o'clock, it reduced to five to seven aircraft an hour, and

it was possible to do it alone.

Top Swiss 935, proceed direct to Torpa.

Direct to Torpa, Top Swiss 935, thank you.

Nielsen manages the safe transit of all aircraft in his airspace.

For further instructions, contact Padua 120.72.

Bye-bye.

Air traffic control is one of the most stressful jobs in the world, and a lot

of it does hinge on decisions made by one person.

Ah, Swiss radar, good evening.

Tillman 611.

Nielsen hears from another plane in his airspace.

Just leveling at flight level 260.

Tillman 611 is the call sign for a Boeing cargo jet owned by the Courier

DHL.

It departed from Bergamo, Italy, and is flying through Swiss, then German

airspace on its way to Brussels, Belgium.

Tillman 611, squawk 7524.

7524. 611.

Tillman 611, climb flight level 320.

Nielsen clears the flight to climb to a higher altitude.

Roger, climb flight level 320.

And requesting 360 thanks if it's available.

Pilots ask for the most efficient flight level that they can fly at. And in this

case, 36,000 feet is much more fuel efficient.

Dillman 611, climb flight level 360.

Climb flight level 360.

Dillman 611.

Nielsen clears flight 611 to 36,000 feet and tracks the change.

You use flight strips to plan the traffic ahead.

With the strips and flight screen we have a good picture of what is going to

happen.

But at 11.30 Nielsen's night shift takes a turn.

Two transmissions come in together, one at the workstation beside him.

There's an Airbus on approach to Friedrichshafen, and another plane

flying at a higher altitude in the upper sector.

Nielsen briefly responds to the Airbus now on approach.

He needs to identify

the aircraft now entering the upper sector.

The aircraft is a

Bashkirian Airlines Tupolev 154.

The Russian plane is slightly ahead of schedule, crossing from Moscow to

Barcelona.

40

-year

-old Oleg Grigoriev is Bashkirian Airlines' chief pilot.

Tonight, he's evaluating the 52-year-old captain, Alexander Gross, who has more

than 10 years' flying experience.

but has flown to Barcelona only once before.

Smooth enough for you?

So far.

It's a bit bumpy back here.

First officer Murat Itkulov, 41, is the captain's second pair of eyes.

Then you better tighten your belt, eh?

The flight is carrying a group of students and some of their parents.

on a school trip to Spain.

As Nielsen gives the Tupolev crew their transponder code.

The Airbus

crew on approach tries to confirm their landing instructions.

As the Airbus gets closer to Friedrichshafen, Nielsen calls the tower

controller to hand off the aircraft.

But he can't get through.

Find me the number for Friedrichshafen Tower.

He tries again.

The desired connection is not possible.

Please check the number. This isn't working either.

Air Lloyd 1135?

Air Lloyd 1135, go ahead, sir.

I lost my phone connection with Friedrichshafen. Can you please call

them on 124.35 and tell them you're coming ILS 24 with 20 miles now?

Okay, will do.

Thank you.

With the approaching Airbus handed off, Nielsen returns to his other aircraft,

the Tupolev passenger jet that's westbound to Barcelona, and the Boeing

cargo jet northbound to Luxembourg.

Nielsen notices that both planes are moving towards each other at 36,000

feet.

Controllers will react.

They will do something to separate aircrafts.

Nielsen realizes that Tupolev is soon scheduled to descend to 35,000 feet.

Bravo Tango Charlie 2937, descend flight level 350.

Expedite, I have crossing traffic.

Descending an aircraft is an automatic response for air traffic controllers

because descending is a lot easier than climbing.

It's the easiest way to solve a conflict.

Bravo Tango Charlie 2937, descend level 350.

Expedite descent.

Expedite descent, level 350.

Bravo Tango Charlie 2937.

Yes, we have traffic in your position now at 360.

Yes,

go ahead.

We've made contact with Friedrichshafen Airport.

But then, as the Aero Lloyd flight signs off...

Affirm. Bye-bye.

Bye-bye.

The Boeing has disappeared from the controller's screen, and the Tupolev's

radar signal is lost.

Bravo Tango Charlie 2-937.

Air traffic controller Peter Nielsen has lost contact with two planes flying over

southern Germany.

Bravo Tango Charlie 2-937.

He called the aircraft and got no response.

He must have understood that it was a collision.

Near the town of Überlingen, people watch as fireballs fall out of the sky.

Huge sections of both planes have crashed to the ground.

There is no shortage of witnesses.

First responders are on site within minutes.

And by dawn, crash investigators from Germany's Federal Bureau of Aircraft

Accident Investigation, the BFU, are there too.

At the accident site, you just document what the wreckage tells you.

The wreckage of the Tupolev is spread over four distinct areas.

There would be maybe 100 meters between some parts.

So it clearly indicates that there must have been an in-flight breakup of the

Tupolev.

Most of the Boeing is found in a forest outside the village of Teisersdorf.

But one section is missing.

The only part of the Boeing that was missing was the vertical tail.

And this later has been found together with parts from the Tupolev.

indicating that the collision took place between the two aircraft.

71 people are dead.

45 of them are Russian students from the city of Ufa.

Investigators soon recover much of the wreckage, including the black boxes from

both planes.

Hey, over here.

But before they get readouts from the black boxes, investigators start to

reconstruct the collision.

So this piece is interesting.

We as accident investigators...

did not have an idea about the details of what exactly happened.

It's red paint.

Could have come from the Boeing.

And then over here.

The main issue is to understand which aircraft part collide with the other one

and which came from the impact to the ground.

Okay, so I've marked all the areas where the red paint from the Boeing

transferred onto the Tupolev.

And we even found part of the Boeing's rudder embedded in the Tupolev right

here.

The only way this could have happened is if

the Tupolev flew straight into the Boeing like

this.

The question is, how can it happen that two planes are at the same place at the

same time?

Thank you.

Okay, so we've compiled all of the radar data from air traffic control.

Okay. Let's see what happened.

Both planes are cruising at 36,000 feet.

They both start descending.

At exactly the same time.

Neither one is trying to get out of the way.

90 degrees at the same altitude is about as simple as it comes. A turn, a descent

of one, a climb of one.

So, how did we get to this point?

It doesn't make sense.

Why would... both planes descend.

We all were of the opinion that the air traffic control system in Europe would

be very, very safe.

So it was really hard to understand that an accident like this could occur.

Let's explore this.

Look at the weather data.

The basic way for pilots to avoid collisions is called see and avoid.

The pilots look out the window, see the other aircrafts, and don't collide.

It was a clear night.

No moon at the time of the collision.

The sky was pitch black.

Even with anti-collision lights, judging altitude and distance would have been

impossible.

For jets operating at high altitudes, moving at seven miles a minute, finding

some little dot even in a clear sky, is nearly impossible.

So, we can eliminate that.

What about ATC separation?

Can we interview the controller yet? We're making arrangements to speak with

him about the accident.

And where are we at with the TCAS recovery?

I'll check.

The TCAS, or Traffic Collision Avoidance System, uses transponders on the

aircraft to transmit a plane's location to others.

If two aircraft appear to be on a collision course, an alarm sounds,

warning pilots to change course.

TCAS is intended for when we need a last-ditch effort to just keep them from

hitting.

Yeah. Thank you.

We've got the tubal of TCAS, but no lock on the Boeing. It's too damaged.

The major question for us, did the TCAS computer work as per design?

The TCAS computer of the Boeing was destroyed completely, and that was a

problem.

If TCAS is at fault...

It could threaten the safety of air travel throughout the world.

Investigators looking into the Uberlingen mid-air collision examined

the TCAS data from the Tupolev plane to determine if it was working properly.

Wait a sec.

The Tupolev's TCAS recorded data for both planes.

There's an identical set of files for both flights.

That was a big moment in the course of the investigation, and we were very

happy about that.

Investigators compare the TCAS altitude data with the radar data from both

planes.

The altitudes match perfectly.

What instruction did TCAS give each plane?

Start with the Boeing.

Did TCAS provide each aircraft with the proper instructions to avoid each other?

Told them to descend.

Which the Boeing did.

Now the Tupolev.

Investigators discover that TCAS correctly advised the Tupolev pilots to

climb.

But they descended.

Just like the Boeing.

So why didn't they follow the TCAS instruction?

TCAS did what TCAS should have done.

If pilots would follow the TCAS instruction, TCAS would have prevented

the accident.

Investigators turn to the Tupolev's Cockpit Voice Recording, or CVR.

to determine why the Russian crew disobeyed the TCAS instruction.

Look here.

On the VSI.

There's a plane approaching on our left.

They first became aware of the Boeing two and a half minutes before the

collision.

They're still more than 25 miles apart.

It's ample time to avoid the Boeing.

So, why didn't they?

We have the same altitude.

It's coming towards us.

No, he has a parallel heading.

For the next minute and a half, the crew discusses the Boeing's position.

Visually.

This is showing us zero.

Zero on the TCAS means there is no difference in altitude between them and

the approaching Boeing.

They seem unsure if the Boeing is actually a threat.

Agreed. But TCAS should warn them if the Boeing is getting too close.

Traffic. There it is!

50 seconds before impact, the TCAS issues the first oral warning when the

oncoming plane is less than 10 miles away and closing fast.

Moments later, the crew receives an instruction from air traffic control.

Descend.

Followed by a different instruction from TCAS.

The crew got conflicting instructions.

TCAS told the crew to climb.

The controller told them to descend.

It says climb.

The controller is guiding us down. Descend?

Really? We're going to descend?

The captain follows the chief pilot's command and puts the plane into a steep

descent. Bravo Tango Charlie 2937, descend level 350.

Expedite descent.

Descend level 350.

Bravo Tango Charlie 2937.

Yes, we have traffic in your position now at 360.

Moments from disaster, TCAS issues a final command.

But it comes too late.

There we have it.

The chief pilot followed the controller's instruction to descend

instead of the TCAS's instruction to climb.

Each one of these guys got TCAS training.

They should have known the TCAS is the final authority.

So... Why did the chief pilot listen to the controller instead of TCAS?

Investigators of the Uberlingen disaster examined the TCAS training of the

Russian crew to determine why they followed the ATC instruction instead of

TCAS. Hey, I think I found something.

TCAS 2000 is intended as a backup to visual collision avoidance, application

of right-of-way rules, and ATC separation services.

A backup?

Look at this.

For the avoidance of in-flight collisions, instructions issued by ATC

is the most important tool.

TCAS is an additional instrument.

So if it comes down to TCAS versus ATC, the Russian pilots go with the ATC's

instructions? It seems that way.

We asked Russian flight crews, and pilots told us, yes, it's a backup for

ATC. And so they explained that the flight crew of the Tupolev did what they

should have done.

But the Boeing crew...

followed the TCAS instruction.

I wonder if they informed the controller

they were descending.

Did the controller know the Boeing was also descending?

Call you back shortly.

Let's have a listen to the cockpit voice recording.

For the flight crews, there's a clear operating procedure.

As soon as possible, they have to report it to ATC.

That was the reason why we had to listen to the Boeing cockpit voice recorder.

Ah, Swiss radar, good evening.

Tillman 611.

Tillman 611, climb flight level 360.

Climb flight level 360.

Tillman 611.

The flight is uneventful.

Right up until a minute before the collision, First Officer Brant Campione

sees an opportunity to take a quick break.

Just gotta use the facilities.

Handing over.

Okay, taking over.

Captain Paul Phillips takes control of the flight.

Is there anything I can get you?

No.

That's the TCAS's first conflict alert.

Descend.

Descend.

Descend.

Descend.

Traffic. Right there.

Yep. Fifty seconds before the collision, TCAS warns the Boeing crew of the

Tupolev's approach.

Increase descent.

Increase descent. Increase? Increase descent.

Increase descent.

Doma 600, TCAS descent.

No doubt about it. They informed the ATC that they were descending.

Let's hear the rest.

Increase descent.

Descent!

Descent board!

So the Boeing crew did nothing wrong. They followed TCAS and informed the

controller. But the controller instructs the Tupolev to descend twice.

Warns them about the crossing traffic.

And then immediately, the Boeing reports it's descending.

He's still got two planes on a collision course.

He's already been talking to the Tupolev crew, so why didn't he just tell them to

change course and climb?

If the controller knew the Boeing was descending, why did he let the Tupolev

also descend?

A major part of the investigation was to identify what the controller did and how

he did perform his job.

Did Peter Nielsen's actions play a role in the Oberlingen mid-air collision?

Bravo Tango Charlie 2937, expedite descent.

Investigators listened to Peter Nielsen's radio transmissions to

determine how two planes on his watch could have collided over Oberlingen,

Germany. Let's start 30 seconds before the collision, when the Boeing pilots

informed the controller of their descent.

Descending flight level 7-0. Aero Lloyd 1-1-3-5.

It sounds like the controller was talking to a third aircraft.

Just as the Boeing aircraft advised the controller of their TCAS descent.

Dillon 600, TCAS descent. Aero Lloyd 1-1-3-5.

Yes, go ahead.

The controller received a simultaneous message from another aircraft.

We've made contact with Frederick Chafin Airport.

So the call from the Boeing crew came in at exactly the same time as the

controller was dealing with the Aero Lloyd flight.

When the Boeing pilots mentioned TCAS descent, he probably didn't even hear

it, or it just was something that he didn't process as an issue, thinking

that everything over on that airspace was already taken care of.

But juggling three planes isn't unusual.

There's got to be more to this.

Investigators listen to earlier parts of the ATC recording.

They

hear

the Tupolev and Aero Lloyd flights competing for Nielsen's attention.

Call you back.

Station calling. Say again, please.

Ah, Zurich. Good evening.

Bravo Tango Charlie 2937.

Level 360.

Aeroloid 1135.

Aeroloid 1135, descend flight level 70.

During the last five minutes before the collision, the workload increased very

much.

Investigators hear Nielsen having difficulty contacting the airport where

the Aero Lloyd flight was due to land.

Find me the number for Friedrichshafen Tower.

How many times does he try calling Friedrichshafen?

Seven. He spent a lot of time on something that should have taken

seconds.

So how did he end up in this situation in the first place?

Normally an inbound call is just a few seconds.

But dealing with the communication system took a lot of time that then

allowed the two collision aircraft to get ever closer at this very high rate

of speed.

Thanks for coming in.

Investigators interview Peter Nielsen to assess his workload on the night of the

accident.

So at the time of the accident, you seem to be working two different

workstations. Why?

There are two controllers on the night shift, but one controller always takes a

rest as traffic decreases for the night.

You're off?

See you in a few hours.

They come back in the morning when traffic picks up.

And is that standard procedure?

It's not written down anywhere in company policies, but management lets us

do it.

Okay.

So, 13 seconds before the collision, the Boeing radioed that they were doing a

TCAS descent.

Did you hear that transmission?

No, I didn't.

I guess I was dealing with the airloid flight approaching Friedrichshafen.

Couldn't get through to the airport. The phone was down for some reason.

Is there anything else you can think of that might help us?

Yeah.

Normally the computer system issues an alert well before two planes get too

close together.

But I never got that alert.

The air traffic control radar system has what's called conflict alert system.

It's looking at the airplanes and based on their current speed and altitude and

heading is projecting out to see if airplanes are coming into conflict with

each other.

The controller was under very high pressure during the last minutes.

It was, at the end for him, a really difficult situation.

Was Peter Nielsen fully equipped to prevent the collision that cost the

lives of 71 people?

Investigators interview officials from Sky Guide to find out why Peter Nielsen

never received a warning of the impending collision above Oberlingen,

Germany.

Why were the control systems, conflict alerts, and telephones both down?

What's this?

A work order for a computer upgrade.

A new software was to be implemented on the main screen, which meant that the

controller had to work on the backup system.

The software in the telephone system also had to be updated.

So is this why there was no phone or visual conflict alert?

Yes.

But it doesn't say that anywhere.

Was Nielsen warned about this before his shift?

Not that I'm aware.

One other thing.

Why does management allow one of the controllers working nights to be on

break most of the shift?

It started when there were three controllers at night But there are only

two now We didn't change the practice

Thank you

That was the way they did it One

controller on screen and the other was on break.

And this was accepted by the management.

Bravo Tango Charlie 2937, descend flight level 350.

It says climb.

The controller is guiding us down.

Descend? Really? We're going to descend?

Investigators now understand.

Bravo Tango Charlie 2937, descend level 350.

Expedite descent.

Expedite descent, level 350, Bravo Tango Charlie 2937.

Why two flights... Descent!

Descent board!

...ended in disaster.

While completing their final report... BFU, hello.

What?

The story of the Oberlingen mid-air collision takes another tragic turn.

On February the 24th, 2004...

Almost two years after the Uberlingen disaster, Peter Nielsen is murdered in

his front garden.

His wife and three children are witnesses to the crime.

We couldn't believe it.

We couldn't believe it because it was for us like a TV story and it was not a

real life, but yes, it was real life.

Did they catch the killer?

Yeah.

Apparently his family was on the Tupolev.

A Russian man, Vitaly Kaloyev, is arrested for Peter Nielsen's murder.

Kaloyev's wife and two children were killed in the Uberlingen collision.

He tells police he went to Nielsen's house seeking an apology.

But Nielsen isn't found at fault for the collision in the BFU's final report.

Instead, it concludes he was unable to safely carry out the tasks required of

him.

The BFU points to the fact that Nielsen was working alone as a cause for the

accident.

Bravo Tango Charlie 2937, descend flight level 350.

Expedite, I have crossing traffic.

Descend.

But the report also highlights deficiencies in aviation regulations

that allowed for the Russian pilots confusion over the use of TCAS. It says

climb. The controller is guiding us down.

Descend? We're going to descend?

The BFU's most prominent recommendation is simple.

Pilots have to follow the TCAS instruction.

not to follow the ATC instruction because TCAS is a safety net.

Eventually, four Sky Guide middle managers, who weren't even working the

night of the Uberlingen disaster, are convicted of negligent homicide.

This accident, it was really a watershed event.

A lot of things had to fall into place just the wrong ways for this to occur.

And it changed a lot of things.

A lot of the way people looked at ATC, collision avoidance, and it really woke

a lot of people up.

In 2005,

Vitaly Kaloyev is convicted of the premeditated homicide of Peter Nielsen.

Two years later, he's released from prison.

Today, nine steel pearls representing a torn necklace mark the locations where

victims' bodies were found.

And a memorial inside Sky Guide marks both the date of the collision and that

of Peter Nielsen's murder.