Original subtitles

(alarm sounding)

- We just lost 1 and 2.

(narrator): All four engines shut down on a jet headed straight for a U.S. suburb.

- It takes a few things to make an engine run, and one of them is fuel.

- Everyone, we're about to evacuate the plane. Remain calm.

(narrator): In Japan, a plane catches fire

with all 165 passengers and crew still on board.

- The only time you have too much fuel on board the aircraft

is when you're on fire.

- We just lost an engine!

- Hang on.

(narrator): And the crew of a 737 are forced

to make a crash landing in the Amazon jungle.

- Something is very, very, very wrong here.

(narrator): Three mysterious accidents send investigators hunting for clues.

Is it possible these tragedies all share the same cause?

- Mayday, mayday!

- It's going up!

(indistinct radio chatter)

(narrator): United Airlines Flight 173

is 22 miles away from Portland International Airport.

The 189 passengers on board are returning home after the holidays.

- United 173 would like clearance for an approach into 28 left now.

(narrator): Captain Malburn McBroom, a Second World War veteran,

is one of United's most experienced pilots.

First Officer Rod Beebe has more than 5,000 hours' flying experience.

Flight Engineer Forrest Mendenhall is the third crew member.

- Okay.

(narrator): He's tasked with monitoring the DC-8's engines.

The flight began in New York City with a stopover in Denver.

- United 173 heavy.

Okay, roll out, heading...

010 to runway 28 left.

(narrator): Air-traffic controller Ed Kingrey

clears flight 173 to land.

Suddenly, an alarm sounds in the cockpit.

- We're losing an engine. (beeping)

It's flamed out.

- You're gonna lose #3 in a minute, too.

(narrator): Two of the plane's four engines have just shut down.

- You gotta keep 'em running, Frosty. - Yes, sir.

(narrator): The engineer struggles to keep the last two engines running.

- How far do you show us from the field?

- I'd call it, uh... I told him it's 18 flying miles,

which would include the base leg to the final,

and then the turn to final to the end of the runway.

(alarm sounding) (automation): Airspeed low.

- We just lost 1 and 2.

(narrator): Flight 173 has now lost all four engines.

With the aircraft dropping by more than 3,000 feet a minute,

Captain McBroom makes a horrifying calculation.

- We can't make it.

- We can't make anything.

- Okay, declare a mayday.

- Portland Tower, United 173 heavy. Mayday. The engines are flaming out.

(narrator): McBroom needs to find a safe place to put the aircraft down

and try to save the lives of all on board.

- I could see him coming in from the south,

his navigational lights flashing.

You could tell he was quite low.

(passengers screaming)

(screaming)

I saw the bright flash out there,

and, uh, and knew he had gone down.

(narrator): The DC-8 has crash-landed in a wooded suburb in Portland, Oregon.

(dog barking) Eight passengers and two members of the crew are dead.

Incredibly, 179 people survive.

(news): A United Airlines plane crashed five miles southeast of Portland Airport,

in a residential area.

Two homes were hit, one disintegrated.

(narrator): The next morning,

investigators from the National Transportation Safety Board are on the scene.

One of the team members is Human Factors Specialist Alan Diehl.

- When I saw how close he'd come to apartment complexes,

I realized this could've been one of the worst accidents in history.

(narrator): Investigators hope survivors can provide some insight

into what brought this jet down.

- When did you first notice something out of the ordinary?

(narrator): They learn from the passengers that an hour before the crash,

the captain made an announcement.

- Ladies and gentlemen, this is your captain speaking.

(narrator): The crew were having trouble with the landing gear.

(Captain): We're not sure whether or not it's working correctly.

We'll be running a few routine checks.

(narrator): But something isn't making sense to Diehl.

- How does a landing-gear problem bring down a plane?

(narrator): At the crash site, the plane's flight recorders are recovered.

They're sent for analysis at the National Transportation Safety Board headquarters

in Washington.

While they wait for the flight data,

investigators continue to speak to witnesses,

including Ed Kingrey,

the controller who handled Flight 173's approach.

- I cleared 'em for an approach to runway 28.

I was about to hand 'em off to the tower controller.

- Uh, negative. We'll stay with you.

We've got a gear problem. We'll let you know.

- He basically said he'd stay with me, that...

he was having some kind of, uh, unsafe-gear indication.

(narrator): Captain McBroom wanted time to troubleshoot the gear problem.

So Kingrey cleared Flight 173 to fly a holding pattern south of the airport,

over the Portland suburbs.

- A holding pattern would basically give him...

his own airspace there to do whatever he had to do.

(narrator): But Flight 173 circled Portland for an unusually long time.

- They continued circling for about an hour.

(narrator): The pilots then made a shocking call to the Portland Tower.

- I recall hearing...

the captain tell the tower they're losing engines.

There was no indication to me,

uh... the gravity of the situation.

(narrator): What happened during that hour of circling

that turned a landing-gear malfunction...

- We've got a gear problem. We'll let you know.

(narrator): ...into a catastrophic engine failure?

- The engines are flaming out. We're going down.

We're not gonna be able to make it to the airport.

- I was clearly very interested in, you know,

how a highly experienced captain could, uh, fly around for over an hour,

in sight of the airport, in good weather,

and not put this airplane on the ground safely.

(narrator): NTSB investigator Dennis Grossi joins the effort to find out what went wrong.

- I was assigned to be the...

aircraft performance engineer for this accident.

Okay, let's go.

(narrator): If there was a malfunction,

he hopes the cockpit voice recorder picked up the pilots discussing it.

- Ladies and gentlemen, this is your captain speaking.

(narrator): The recording begins 30 minutes before the crash

as the pilots circle over Portland.

- ...because I only got this thing to shine down there.

(narrator): They hear the flight engineer leave the cockpit

to troubleshoot the landing-gear problem. (alarm sounding)

When the landing gear is lowered,

a small rod pops up in the wing,

providing visual confirmation that the gear is in place.

- The flight engineer would be asked by the captain to go back and check

the mechanical indicators for the position of the landing gear.

- Excuse me. Can I look out the window here?

- And he could look over, and there are tabs that actually come up and go down,

and he could see if the gear was extended and locked.

- How's that main gear back there?

- Uh, both appear to be down and locked.

(narrator): Despite his engineer's report,

Captain McBroom still sounds concerned. (alarm sounding)

- There's one check we missed.

Checking the gear warning horn.

- Uh-huh. Right.

- Right. - Right.

- Normally, when we see these problems of a gear light not coming on,

it's a light bulb or some minor piece of circuitry.

(narrator): It appears that a minor electrical problem

became a major distraction for Captain McBroom.

But it still doesn't explain why all four engines were out.

Then investigators make a shocking discovery.

- Losing an engine. It's flamed out.

- Why?

- Fuel. (captain sighing)

(narrator): The cockpit voice recorder from United Flight 173 reveals

that the captain is unaware that his plane is running out of fuel.

- He was asking what was causing that,

and he got a very adamant answer saying: fuel.

- Fuel. - As if to say:

We've been trying to tell you about this all along.

- Number 2 is empty.

- You're gonna lose 3 in a minute, too.

(narrator): One by one, fuel starvation shuts down all the engines,

leaving the DC-8 without any power.

- Okay, declare a mayday.

- How could an experienced crew lose track of how much fuel they had on board,

and in fact run out of fuel

when they were in view of the airport?

(narrator): Captain McBroom may be the only one who can provide answers.

He's in hospital recovering from injury,

but well enough to speak to investigators.

(alarm sounding)

- I recall...

seeing #1 and #2 warning lights come on,

but I...

I knew we had fuel.

- He was still convinced that somehow,

the fuel had either leaked out of the tanks,

or the fuel burn was too high, or the gauges were wrong.

(narrator): Investigators wonder if the fuel gauges were malfunctioning

and confusing the pilots.

To find out, investigators study the transcript of the cockpit voice recorder,

focusing on the pilots' discussion of fuel levels.

- The crew discussed how much fuel do we have. We have 5,000 pounds.

You take the data and apply the time factor to it,

and you can figure out how much fuel they should've had remaining.

- Five thousand. That's exactly right.

(narrator): The team discovers there's nothing wrong with the gauges.

Flight 173's fuel system was working exactly as it should.

With mechanical failure ruled out,

the team now explores the human factors,

specifically Captain McBroom's behaviour.

- How much fuel you got now? - Four. Four.

(narrator): Investigators play back the cockpit voice recorder

to study his performance.

- How much fuel you got now?

(narrator): They hear something alarming in the conversation. (alarm sounding)

- How much fuel we got now? - Four. Four, uh, thousand, in each, pounds.

- Both the first officer and the second officer...

...were acutely aware of the fuel status.

(narrator): His crewmates tried more than once to alert him to the fuel situation.

But McBroom is focused on the broken landing gear.

- There's one check we missed.

Checking the gear warning horn.

- Uh-huh. Right.

- Right. - Right.

So how do we do that?

- Flying with a very senior captain,

it would be very difficult to challenge that captain in those days, uh,

about something like fuel.

- The captain was so focused on the gear collapsing that he lost the big picture.

- They lost sight of the real emergency, which was the lack of fuel.

(narrator): Captain McBroom's obsession with the landing gear,

along with his crewmates' failure to speak up,

caused the plane to run out of fuel and crash in the Portland suburb.

- After this accident, the National Transportation Safety Board

said flight crew members need to be better trained to communicate

when they have safety-of-flight issues.

(narrator): In a move that has a lasting impact on airline safety,

the Federal Aviation Authority adopts a training system developed by NASA,

known as Cockpit Resource Management, or CRM.

- It teaches captains to listen better,

and it teaches the other members on the flight deck to be respectfully assertive.

(narrator): If the crew of Flight 173 had received CRM training,

they might have insisted that Captain McBroom land immediately.

- Not enough. Fifteen minutes is really gonna run us low on fuel here.

(narrator): Instead, they expected their captain to make the right decision.

- Had it not been for this investigation,

I'm pretty sure that Crew Resource Management would have taken place,

but at some point in the future,

and very likely other aircraft would've crashed in the interim.

(narrator): In 2007,

a terrifying explosion reminds investigators

that catastrophic fuel failures don't just happen in the air.

(narrator): China Airlines Flight 120 is on final approach for landing

in Okinawa, Japan.

(chiming) (captain): Ladies and gentlemen,

we're about to begin our descent into Okinawa Naha Airport.

Please give the flight attendants your full cooperation

as they prepare the cabin for landing.

(narrator): The captain is 47-year-old Yu Chien-Kou.

- What's the weather for approach?

- Cloud ceiling is 8,000 feet. Winds at eight knots.

(narrator): The first officer is 26-year-old Tseng Ta-wei.

The pilots have more than 8,500 hours of flight experience between them.

This morning, there are 157 passengers and eight crew on board.

- Please put your tray up and fasten your seatbelt.

(narrator): The pilots reconfigure their plane

as they slow down and descend for landing.

- Let's go to flaps 25.

- Flaps 25.

(narrator): They deploy flaps from the wings' back edge,

along with slats from the front edge.

These devices keep the plane airborne at lower speeds.

(automation): 30, 20, 10.

(narrator): It's a textbook landing.

- Flaps in.

(narrator): All that's left for the China Airlines pilots is to park the plane.

- Engine start levers.

- Engine start levers cut off.

- Seatbelts. - Seatbelts off.

(narrator): Then one passenger notices that something's not right.

(Speaking Japanese)

(alarm sounding) - Hey, what is this?

- What's happening?

(narrator): Just when they thought they were safely parked...

- Cockpit, ground. Number 2 engine fire.

(narrator): ...a radio call alerts them to a fire in the right engine.

- Dynasty 120, we are calling a fire truck. Remain... Stand by.

(shouting in Japanese)

- Cabin crew, prepare for evacuation.

Prepare for evacuation.

(narrator): Within minutes, the fire engulfs both wings.

- No pushing, no pushing.

(narrator): Flight attendants work to evacuate the passengers as quickly as possible.

The plane could explode at any moment.

- Captain, all passengers are evacuated. You're the last ones.

(coughing)

(narrator): But it may be too late for the pilots.

Thick smoke is consuming the cabin,

so they will have to escape through a small cockpit window.

- You first. - Yes, sir.

(people screaming) (man): Oh! Whoa!

(narrator): Incredibly, both pilots evacuate just in time.

All 165 people on board escape unharmed.

- I've never heard of any evacuation where somebody wasn't hurt.

To get this many people off in such a dire circumstance

in a very short period of time with no injuries is miraculous.

- It's highly unusual for an aircraft to catch fire at that phase of flight,

so, uh, that sparked a great deal of interest.

(indistinct radio chatter)

(narrator): A team of international air-crash investigators

are immediately called in.

They need to find the cause before there's another deadly explosion.

Across the globe,

there are more than 5,000 Boeing 737s in service.

- There's a 737 taking off and landing

every three or four seconds in the world.

(narrator): Knowing countless passengers could be at risk,

investigators race to figure out how an airliner that landed safely

suddenly burst into flames.

- Okay, let's get to work!

The challenge for the investigator is...

most of the evidence will be destroyed by the fire.

(narrator): While recovery workers collect the scorched wreckage,

the team begins interviewing eyewitnesses.

- What did you see?

(narrator): A ground worker who saw the explosion provides a critical detail.

- The ramp worker on the right side of the aircraft

said very distinctly that he saw a liquid

running down the leading edge of the right wing before the fire broke out.

- Thanks.

(narrator): Fluid leaking from this part of the wing of the aircraft

can only be one thing:

Jet fuel.

The Boeing 737 holds 4,390 gallons of fuel,

much of it in tanks located inside the plane's two massive wings.

- When we figured out that an actual fuel leak had occurred,

it was a breakthrough, a true breakthrough in the investigation.

- We know the fuel was leaking, but from where?

(narrator): Investigators examine what remains of the 737's fuel tanks.

The tanks are made from aluminum alloy and should never crack or leak.

They use a small camera called a borescope

to see inside the right fuel tank.

What it reveals changes the course of the entire investigation.

- Whoa. Would you look at that?

(narrator): While examining the right fuel tank of China Airlines Flight 120,

investigators find a bolt lodged in the side of the tank.

- All of a sudden, clear as a bell,

we saw this bolt sticking out of the fuel tank itself.

(narrator): The bolt has ruptured the tank,

right where the ground worker spotted leaking fuel.

- It's hard to describe how significant this was.

I mean, this was the core of the investigation.

(narrator): But where did the bolt come from?

- Okay. Got it.

(narrator): Investigators compare the piece to schematics of the 737 wing structure

to figure out exactly what it is.

They soon get their answer.

- A downstop assembly.

(narrator): The downstop assembly

is part of the slat mechanism on the wing's leading edge.

- Let's go to flaps 25.

- Flaps 25.

(narrator): Pilots extend flaps and slats during every takeoff and landing.

The downstop is fixed to the end of a track that slides back and forth.

The device prevents the slats from moving too far forward.

- We had the assembly. We knew it punctured the tank.

Our next step was trying to figure out how this could possibly have occurred.

(narrator): When comparing the downstop assembly from Flight 120

to Boeing schematics...

...the team uncovers a vital clue.

- We decided to count parts,

and lo and behold, a washer was missing.

(narrator): There's supposed to be a washer right behind the nut.

- Where is it?

(narrator): Could a single missing washer have played a role in the accident?

- Alright. Now let's test it without a washer.

(narrator): The team experiment with the suspicious bolt from Flight 120

to see how it performs without the washer.

They make a stunning discovery.

The small washer is the only thing preventing

the unit from falling out of its mount.

- Without the washer... it fails.

(narrator): Investigators need to find out how the part could've disappeared.

- We went to China Airlines

to ask them to demonstrate how they do... the maintenance work.

- Sometimes maintenance records don't tell you the true story.

(narrator): They learn a repair was ordered on the downstop a few weeks before the accident.

A mechanic demonstrates how he performed the repair.

- After applying glue... you put the bolt into place.

(narrator): But reaching the downstop's location proves challenging.

- You can imagine that you're under the wing and you cannot see it.

- Sorry. I just dropped it.

Don't worry. It's easy to pick up again.

(narrator): It's an eye-opening demonstration.

- It's not very easy for them to confirm

they finished their job and everything is in order there.

(narrator): Investigators believe the washer must've fallen off

during the maintenance procedure in Taiwan.

The sequence of events that led to the devastating fuel fire in Okinawa

is finally clear.

Six weeks after the failed repair of a downstop...

- Please give the flight attendants your full cooperation

as they prepare the cabin for landing.

(narrator): A descent into Okinawa requires the pilots

to deploy the flaps and slats as usual.

Inside one of the track assemblies on the right wing,

the loosened bolt without a washer is just barely holding on.

Touchdown is enough of a jolt to finally knock it out of its track.

- Flaps up.

(narrator): The unsuspecting crew soon retracts the flaps and slats.

The plane's powerful hydraulics move the slat track back into place.

But now the downstop bolt is in the way.

The track pushes it to the back,

puncturing the right-wing fuel tank

and causing thousands of litres of fuel to leak.

- After-landing checklist.

(narrator): Once the pilots park and shut down the engines...

...the leaking fuel starts dripping directly onto the scorching-hot tail pipe,

igniting on contact.

In the wake of the China Airlines explosion,

aviation authorities around the world

order the inspection of the entire fleet of 737s.

In the U.S. alone,

21 planes are found to have the same defect,

all of them at risk of a catastrophic fuel leak and fire.

Boeing takes immediate action.

It redesigns the downstop mechanism

and ensures that the improved part is installed

on each and every plane.

- In today's aviation, the failure of any kind of component part,

especially as it relates to a fuel system, is a rare event.

You stand a better chance of survival

if you have a catastrophic event on the ground.

But as the airplane goes up, so does the risk level.

(automation): Terrain. Terrain. (narrator): In Brazil,

investigators uncover another fatal problem

when a disastrous fuel failure brings down a plane in the Amazon jungle.

(narrator): Brazil in the late 1980s is a country in transition.

Developing cities are scattered throughout the dense Amazon rainforest.

In Marabá, the crew of Varig Flight 254 is preparing for takeoff.

- Exterior check complete.

(narrator): There are 48 passengers on board.

Flight 254 is an hour-long flight from the mining town of Marabá

to Belém, near the mouth of the Amazon River.

The crew dials in a compass heading to guide them to their destination.

- Here we go.

(narrator): Captain Cézar Garcez is flying the airplane tonight,

while First Officer Nilson Zille monitors the instruments.

- V1.

Rotate.

(narrator): The Boeing 737 steadily climbs to cruising altitude.

After 23 minutes, the flight computer tells the captain

that they're getting close to Belém.

- Looks like we're nearly there. - Mm.

Belém Tower, Varig 254, requesting descent.

Belém Tower, Varig 254.

- Belém Tower, do you read?

(narrator): Strangely, they get no response from the tower.

- Let me try. Belém Tower, Varig 254.

- Hmm. That's funny.

- What?

- We're not picking up the beacon either.

(narrator): Airports are equipped

with Very High Frequency Omnidirectional Range beacons, or VOR beacons.

Their signal guides incoming aircraft to the runway.

- I'll call the tower on HF.

(narrator): The captain switches his radio to high frequency and tries making contact again.

- Belém Tower, Varig 254.

(narrator): Thankfully, his strategy works.

- Varig 254, Belém Tower. Go ahead.

- Belém, we're on approach, but we aren't seeing the VOR. Is the beacon down?

- Negative, 254. Looks like it's on your end.

- Understood.

(narrator): The crew will have to approach Belém

without the help of the VOR signal.

The captain checks his system and calculates when they'll arrive.

- Belém, we're 25 minutes out.

Request descent for final approach.

- Roger, Varig 254.

Cleared to flight level 2-0-0.

(narrator): As the plane drops below the clouds,

the captain looks for the lights of Belém.

- Where are the lights?

Where's the airport?

(narrator): But there's only darkness.

- No visible lights, Captain.

(narrator): In Belém, the controller is concerned.

Flight 254 should have landed by now.

But he doesn't have a radar, so he has no way of tracking the plane.

- We need to land soon, or else we're gonna run out of fuel!

- I think we're close.

(narrator): The captain searches for a local radio signal,

hoping it will guide them towards the city.

- Now we can follow the signal towards Belém.

- Turning right, heading 1-6-5.

(narrator): After 2.5 hours in flight,

the captain is confident he's now on course.

- There we go.

We're over the Amazon now.

(narrator): Belém is near the mouth of the Amazon.

Following the river should lead the pilots to the city.

But seconds later... (alarm sounding)

- We've got a fuel warning!

(narrator): ...Flight 254 is running out of fuel.

The pilots suddenly realize they can't make it to Belém.

- Flaps to 2. We need to do a controlled descent.

(narrator): They'll have to make a forced landing in the dense Amazon rainforest.

- We just lost an engine!

- Hang on. (alarm sounding) I'm going to put her down.

- There goes the other one!

(narrator): The inevitable impact is just seconds away.

(automation): Terrain. Pull up. - Just... need... to...

bring us down!

Nice... and... slow!

(alarm sounding) (automation): Pull up.

(narrator): Of the 54 passengers and crew, six die on impact.

Many are badly hurt, including First Officer Zille.

(baby crying)

The captain tends to the wounded while they wait to be rescued.

- Ah! (clattering) (man): Help.

(narrator): But no one in the outside world knows where the plane has gone down.

(narrator): Investigators conduct an aerial search around Belém

for Varig Flight 254.

But there's no sign of the missing aircraft.

(interpreter for Machado): You get anxious to find the plane quickly,

because people have a better chance of survival during the first 48 hours.

After that, survivors are more likely to die.

(narrator): After two nights in the jungle,

a small group sets off to find help.

Hours later, they stumble on a farmhouse.

- They found survivors!

(interpreter): It's sort of a relief to realize the scenario is not as tragic,

and there's an urgent desire to get to the location and start to work.

- Where did you say they are?

(narrator): The crash site is nowhere near Belém.

- It came down right... here.

(narrator): The wreckage of Flight 254 is lying in the Amazon jungle,

nearly 700 miles away.

- How on earth did they get way over there?

No wonder we couldn't spot the beacon.

It's nowhere near the destination.

(narrator): Within hours,

Brazilian military reach the remote crash site of Varig 254.

They find 43 survivors.

Five people have died waiting for rescue, and another dies soon after.

Shortly after the rescue efforts, there's a major breakthrough:

the discovery of the plane's two flight recorders.

Investigators hope they will reveal why Flight 254 was so badly off course.

(interpreter): We were relying on the two flight-data recorders.

Both pilots were alive, so we thought we were certain to come to a conclusion.

(narrator): But when investigators review the flight data,

it paints a confusing picture.

Instead of flying north to Belém,

the plane took off west and flew in the wrong direction the entire flight.

(interpreter): This became a central focus of the investigation,

to know why the aircraft was so far off course.

(narrator): Investigators wonder if the crew were given the wrong navigation details.

Thankfully, Flight 254's flight plan from the airline

is among the documents recovered from the cockpit.

- Oh, thanks. Let's see what this will tell us.

I think I know what they did wrong.

(Fox): Their computer flight-plan system has four digits.

This is very, very unusual, as they almost always, uh, have only three.

The number 0270...

was intended to mean...

27.0 degrees.

(interpreter): When we noticed that,

it gave us the idea that instead of entering 027,

which was the heading to Belém, he had entered 270.

- The captain read it as 270 degrees,

or due west, so instead of flying northeast...

- They went west instead,

going 270.

He entered the wrong heading.

(narrator): Flying for more than three hours in the wrong direction...

...investigators suspect the aircraft ran out of fuel,

forcing the crew to make a crash landing in the Amazon.

To confirm their suspicions,

they call in Captain Garcez to tell his side of the story.

- I'll try to help you.

(narrator): Under intense questioning,

he admits he misread the flight plan,

causing the aircraft to fly hundreds of miles off course.

- Look, it was an honest mistake.

(narrator): Company records show the airline began printing their flight plans in a new way

while the captain was on vacation.

- It's easy to see how you'd get confused.

(interpreter): From that moment on,

the cause or the basic framework of the accident was determined.

(narrator): But the first officer was also required

to enter the heading from the flight plan.

Why didn't he catch the captain's mistake?

Aviation Psychologist Kathy Mosier provides insight.

- The co-pilot, probably after many experiences with captains

who had always done it right and never had to double-check,

just entered what the captain had put in,

and assumed that it was the right thing. So in this case,

your safeguard is gone, because the co-pilot is not crosschecking.

- The original...

navigation mistake, um, was that of the captain.

What is disheartening here is that both pilots went along with it.

(narrator): Flight 254 was flying in the wrong direction from the moment it took off.

Instead of asking for help,

the captain tried to get back on course using a local radio signal.

He thought he found a station in Belém,

but instead picked up a signal in the opposite direction,

taking them further away from their destination.

(interpreter): His pride prevented him from saying to his colleague:

"Help me. I'm in trouble." That would've been a better approach.

(narrator): While scanning their radar,

the crew thought they spotted the Amazon River,

which would take them back to Belém.

But the river they saw was the Xingu,

more than 600 miles southwest of Belém.

- How could they be so confused for so long?

- I think we're close.

(narrator): Investigators conclude the crew was in the grip

of what's known as confirmation bias...

...the tendency to favour information that confirms something we already believe.

- When I saw the river, I was sure.

I was sure we were close to Belém.

- It just goes to show you anybody can...

fall into decision traps,

and even experts have to always be on guard.

(narrator): The accident report faults both pilots for the actions

that caused the plane with 54 people on board

to run out of fuel and crash in the jungle.

After the crash of Varig 254,

the airline changes their flight plans,

so the decimal place is clearly marked.

They also improve pilot training.

Brazil's national radar system is modernized and expanded to cover the entire country,

making it less likely that a plane would go missing.

- Fuel management in flight is the responsibility

of the pilots in the cockpit.

But you can have those same human errors on the ground.

The big common thread between these three accidents

is the human factor.

It is the responsibility to have not only a knowledge of what you're doing,

but a fundamental understanding so that you can execute properly.

Subtitling: difuze