Original subtitles

(narrator): Above the remote Alaskan wilderness...

(impact)

(screaming)

two planes collide.

- Mayday. Mayday.

(narrator): A witness races to help.

- All I saw was a whole bunch of people floating.

(narrator): Six people are dead.

- A mid-air collision is probably the most scary thing

that can happen to you.

(narrator): NTSB investigators talk to the surviving pilot.

- Look, he was just there. I couldn't avoid him.

(narrator): When they examine the onboard alerting system...

(Bramble): Why didn't he turn away?

(narrator): ...the mystery deepens.

- We're missing something.

(narrator): But then, investigators get an unexpected glimpse...

- Whoa. (narrator): ...into a key moment in time.

- It was eerie and disturbing to see the photos

because they were taken in a person's last moments.

(theme song)

(soft piano music)

(narrator): It is a busy day

at Alaska's Misty Fjords float plane base.

Four cruise ship passengers have booked a sightseeing flight

over Alaska's spectacular southeast coast.

- Okay, folks, get comfortable and fasten your seatbelts.

(narrator): 46-year-old Randy Sullivan is the owner

of Mountain Air Services, and is its only pilot.

- Hey. It looks like you're gonna have the best view in Alaska.

- I can hardly wait. (chuckling)

(narrator): This will be Sullivan's second flight of the day.

- I've just got a few things to do before we get started.

(narrator): Randy Sullivan has spent most of his career

flying over Misty Fjords.

(bright music)

- Transponder on and broadcasting.

Okay, guys, put your headsets on.

(Floyd): Mountain Air was

a small operator doing primarily sightseeing trips.

- Can you guys hear me okay?

Okay, here we go.

(Floyd): This would have been his entire life

running this company and he would have loved

what he was doing.

- Alright.

Flight controls, free and correct.

Master fuel, check.

Landing lights, check.

(narrator): Just after 12 noon,

the Mountain Air floatplane is ready for takeoff.

- Okay, that's five minutes since the last departure.

(camera shutter clicks)

(narrator): Pilots space out their takeoffs

since there's no air traffic control in this area.

(Sullivan): Misty traffic,

this is Beaver 5-2 Delta Bravo ready for a straight-out.

Any conflicting? Misty Traffic.

(narrator): Sullivan radios other pilots in the area.

(Floyd): In airspace like the Misty Fjords,

the pilots all control themselves.

And it's primarily a see-and-be-seen situation.

Without any air traffic control to keep you separated,

you have to maintain that separation yourself.

(narrator): It is a textbook takeoff in light winds.

Today's 40-mile flight will take passengers

from Rudyerd Bay to Ketchikan.

They'll cross high mountains and dramatic terrain.

- The Misty Fjords is an absolutely beautiful area.

It's towering mountains, glaciers,

lakes, fjords, wildlife.

And the best way to see a place like that, of course,

is from an airplane where you can get the full impact of the scenery

and the immenseness of the area.

(soft music)

(narrator): Every year, more than 100,000 cruise ship passengers

visit Alaska's Misty Fjords.

The flight tours have become an essential experience

for those who can afford the luxury price tag.

- If you look out to your left, you'll see cliffs

that were carved smooth by the last great ice age.

(narrator): Randy Sullivan points out the highlights throughout the flight.

- Being a single pilot operation while you're doing the tours,

you're multitasking with your customers all the time

trying to give them the best tour that you can give them.

At the same time, you're also multitasking as a pilot

where you're trying to maintain

your situational awareness of all the other aircraft.

As well as you're a lot of times flying at very low level

through the terrain which adds one more bit of complexity

to the entire operation.

(narrator): Mountain Air Services operates

a De Havilland Beaver, a single-engine prop plane.

The Beaver was originally built

for the United States Air Force in 1951

but many are now operated by northern bush pilots.

(Floyd): The De Havilland Beaver was a uniquely designed airplane.

And the takeoff and landing is absolutely incredible.

That's what makes it so versatile in the bush is that

you can get it in and out of pretty much any little lake.

Uh, if you're on wheels or skis,

you can get it off short strips or short frozen lakes.

(plane buzzes)

- Misty traffic, Beaver 2 Delta Bravo

exiting Rudyerd, climbing through 1,900 westbound.

(radio): Check that.

45 Mike Mike is just off the water now

and well behind you.

(narrator): It's May and this part of Alaska

is enjoying exceptionally good weather.

(Floyd): On the Alaska coast, the weather can change extremely rapidly.

It can go from a beautiful clear day

to just horrible weather within a very short period of time.

When the days are good,

all the aircraft are flying,

everybody is out making hay while the sun shines.

- Have a good cruise so far? - It's been great.

(narrator): The forecast for tomorrow is low clouds and rain.

So today, Sullivan plans to operate a full day of flights.

- You all are pretty lucky.

They call this place the Misty Fjord for a reason.

Weather like this is pretty rare.

(radio): Beaver 8 Golf Mike,

is 2,700 ft in the climb exiting the Bay.

We've got the Mountain Air Beaver ahead.

We will fall in trail behind.

- Hey, Dave. I've got you on display,

but I don't have your visual.

As long as you can see me, we're good.

(radio): I got you above and ahead of me, Randy.

Enjoy the ride.

- Oh. (chuckles)

Even if we can't see each other,

the display lets us know where the other planes are.

- Cool.

- The traffic systems will enhance your ability

for the see-and-avoid because it will alert you of aircraft

that you may have missed because of visibility issues

or you get too close.

(Sullivan): Coming up in about two minutes on your right,

you're gonna see one of the highlights of the trip:

the majestic Mahoney Falls.

(bright music)

(narrator): 20 minutes into the flight,

the Beaver approaches the waterfall.

Passengers are treated to a spectacular view.

(impact)

The Beaver and another aircraft collide.

- The Beaver basically came apart.

It free-fell 3,000 ft from the sky.

(dramatic music)

(narrator): A retired fisherman on George Inlet

is shocked by what he sees.

- Mayday. Mayday,

this is "Hotel C" calling coast guard radio.

(coast guard): Go ahead.

State the nature of your emergency.

(sombre music)

(narrator): The second plane involved is a larger,

10-passenger De Havilland Otter.

- Two float planes down, George Inlet.

(Floyd): The Otter was still largely intact.

There was damage.

The pilot obviously kept his cool

and managed to control the aircraft.

- I saw an Otter float plane

crash into the water with a huge splash.

And I got closer and all I saw

was a whole bunch of people floating in a...

in an area, um, 50-60 yards.

But there was one person, never made it out of the airplane.

(narrator): The 10 survivors, including the pilot,

are rushed to hospital.

There are no survivors from the plane piloted by Randy Sullivan.

How could two planes in one of the most popular tourist locations on Earth

collide in mid-air?

(soft music)

Within hours, the National Transportation Safety Board,

or NTSB, dispatches a team of investigators

to search for wreckage.

- We still have to recover the planes, and then we have

to look at those and it takes some significant work

to really understand how the two came together,

but we have some great experts at the NTSB who are well versed in that.

(narrator): Aaron Sauer is named Lead Investigator.

(Sauer): The wreckage area of the Beaver

was scattered for about 3,000 feet.

Uh, a portion of the main fuselage was located

upside down in the saltwater.

But there was a lot of debris

that was mixed into the terrain,

and that mountainous area.

Vegetation was high.

It was very difficult to navigate to try and recover

as much of the debris from the Beaver that we could.

(narrator): The other aircraft, the Otter,

is owned by the largest tour operator in the area, Taquan Air.

It sank in 80 ft of water.

(Sauer): The floats of the Otter were separated.

They ended up washing ashore.

But ultimately, they were able to get divers down,

locate the wreckage almost immediately.

And they were able to successfully get

that aircraft up on that barge.

(sighs) - Um, Tag the Beaver wreckage,

and when the Otter comes, we can put it there.

(narrator): The small sightseeing planes

were not required to carry black boxes.

- Keep an eye out for avionics, cameras, phones,

anything with photos or data

that'll help us piece this together.

(narrator): Without recorders, the investigation becomes much more difficult.

- So without the cockpit voice recorder

and flight data recorder,

we had to look for other sources of data.

- Hey, help me move this.

(narrator): As the team surveys the Beaver wreckage,

they find evidence that can help them piece together

the violent collision.

(Bramble): These are saw-tooth marks

from a propeller striking the right wing.

(Sauer): We wanted to understand what angle did we have?

That was very important for us to understand

in order to recreate the collision

and aid us in the investigation.

- The pattern's in the inboard direction.

- So the Otter came from behind, and to the right.

(narrator): The discovery begins to unveil

what happened in the skies over Misty Fjord.

(Sauer): The collision angle was important for us

because what it told us is

both airplanes weren't necessarily on a head-on collision course.

They were more or less headed

to the same location with a shallow degree of angle.

The collision was more of a sideswipe.

Both planes took off from Rudyerd Bay here...

and headed to the cruise ship in Ketchikan.

- The Beaver left first.

A few minutes later, the Otter departed.

(narrator): With a basic understanding of how

the two planes collided,

investigators try to pinpoint where the accident occurred.

- We had one witness...

(soft investigative music)

...who was located here.

- We had a witness that was hunting in the area,

that didn't see the collision, but heard the collision,

which then, in turn, gave us an idea of where exactly

did this happen up in a point in the sky.

- Based on his account, the collision happened

somewhere in here.

(narrator): Investigators now know exactly

where the accident occurred, but they still don't know why.

- Maybe they were converging

on this point.

(narrator): The planes collided

very near the scenic Mahoney Falls.

- It is certainly possible.

It has happened before.

(narrator): A similar mid-air collision happened over Arizona in 1986.

A Twin Otter and a helicopter

collided over the Grand Canyon, killing 25 people.

Both aircraft were also approaching a popular scenic attraction.

(Bramble): Air tour flights have a higher rate

of mid-air collisions statistically speaking because

they operate in areas with

dense traffic around various scenic landmarks.

And in addition, they operate

without air traffic control separation.

What was the weather like that day?

- I'll check it out.

(narrator): Did Alaska's rapidly changing weather

play a role in the accident?

- The weather conditions in any accident are important

to understand the environment

that these pilots are operating in.

Are the weather conditions cloudy? Does that limit their ability to see?

Does it limit their ability to react to certain situations?

These are from a weather cam, 8 miles from the accident.

(narrator): Investigators review weather reports

for nearby George Inlet at the time of the accident.

- A few scattered clouds...

but much higher than they were flying.

- Mm-hmm.

(Sauer): The weather conditions in Ketchikan

on the day of the accident were beautiful,

so at that point, we knew that the conditions

were not gonna be a factor in this accident.

- Something else prevented these guys from seeing each other.

(soft piano music)

What if...

the pilots didn't have enough time

to look out the window for other traffic?

- Or maybe the pilots were trying to give

their customers the best view.

(narrator): What prevented the pilots from seeing each other

as they converged on the scenic waterfall?

(Floyd): Flying an aircraft full of tourists

can be a very challenging task.

You have a number of people that all want to ask questions,

they all want to see different things,

especially in an area like the Misty Fjords

where there is so much to see.

- It is a lot for a pilot to do all at the same time.

- Well, the local pilots certainly were concerned.

Enough to create this.

(narrator): Investigators discover a set of guidelines

agreed upon by tour operators

to enhance safety over Misty Fjords.

- The Letter of Agreement between the operators

was intended to help them coordinate their routes of flight

and their callouts so that they could become better aware

of where they would each be operating and avoid each other.

The companies were aware of

this hazard of mid-air collisions

and that they were attempting to implement

some procedural mitigations against this hazard.

- It looks like most aircraft flying tours

also had onboard an ADS-B traffic warning system.

(narrator): ADS-B, or Automatic Dependent Surveillance Broadcast,

is a traffic alerting system

that transmits a plane's GPS location and altitude

to ground stations and other aircraft.

If two airplanes get too close to each other,

an alert is issued in both cockpits.

- When your traffic system tells you

you've got a conflict,

it's gonna have your attention immediately.

It will only tell you that there's a problem when there is.

- Hmm. - It looks like the Otter

had an alerting system installed onboard.

What about the Beaver?

- Yup, it had a system installed on it as well.

(Sauer): It was important for us to understand

which aircraft had which equipment

as far as alerting capability, traffic displays.

Okay, here's the Otter's system.

(narrator): Investigators first examine the Otter,

the aircraft that collided with the smaller plane to its left.

The Otter uses GPS and a radio transponder

to broadcast its altitude and position.

A colour screen inside the cockpit

plots other nearby aircraft on a moving map.

- What did the Beaver have?

- Well, the Beaver pilot had a different system.

It had a tablet to display traffic info.

(Sauer): So we knew that both aircraft were equipped with

some level of traffic display,

so the question was, were they able to function as designed?

(birds chirping)

(Bramble): Ah.

- Let's see what we got.

(narrator): Investigators review whether ground stations

received any GPS transmissions from the aircraft

detailing their locations.

(Bramble): There's the Beaver.

- Misty traffic, Beaver 2 Delta Bravo

exiting Rudyerd climbing through 1,900 westbound.

(Sauer): And there's the Otter.

- Alright, folks, if you look outside your windows

down at the hills below, you might just see some wildlife.

(suspenseful music)

- Both airplanes were broadcasting their position

but they still hit each other. - It doesn't make sense.

- Maybe the system didn't issue an alert?

- The Otter pilot would know.

(Banning): It seems like so many of these investigations

when you have a mid-air are...

are just not survivable.

And so, it was...

it was very fortunate to be able to talk to the pilot.

- Tell me about the flight.

(narrator): Investigators interview the Otter pilot,

Lou Beck, who has just been released from hospital.

- Passengers were happy. Air was smooth.

- Was it busy out there?

- Visually, I never saw anyone else.

- What about the traffic alerting system?

- It was on. I saw targets on the screen, but...

they were well south of me.

Okay.

I've got one 3 miles out, 3 o'clock.

Opposite direction, no conflict.

I flew a longer route than the other planes.

Took me away from most of the regular traffic.

- But you still ended up at the waterfall? - I did.

That's when all hell broke loose.

Okay, folks, in a few seconds,

we're going to arrive at the beautiful--

(impact)

He was just there. I couldn't avoid him.

Hang on, everyone!

(plane rattles violently)

(passengers screaming)

- Was there any alert from the traffic system?

- Nothing. After the impact, I just went into survival mode.

Brace for impact!

Brace, brace, brace!

(plane buzzing)

(crash)

(soft music)

(Bramble): The pilot seemed very attentive

to mid-air collisions as a hazard.

He was aware of the cockpit display of traffic information in the cockpit.

And he recalled looking at it

to scan for traffic before the collision.

- Look, I just want to reiterate that the alert system

did not sound an alert.

- Thank you.

This was very helpful.

(narrator): Investigators are now confident

the collision happened without a warning

to alert the Otter pilot.

The question is why?

(Otter pilot): Hang on, everyone!

- Let's have a look at the Otter's traffic alerting system.

(narrator): Investigators use the ground station data

to recreate what the Otter pilot would have seen

on his traffic alerting system

moments before crashing into the Beaver.

(Sauer): It's painting targets.

There's the Beaver approaching.

- The alert should happen any second now.

(narrator): As the Beaver gets within 2.5 miles,

an alert should sound.

- It's not doing anything. There's no alert.

(curious music)

- It was very surprising to us that the cockpit display

of traffic in the Otter didn't provide traffic alerts

because that's a really important defence against mid-air collisions.

- There is something not right with the alerting function.

- Okay, folks, in a few seconds,

we're going to arrive at the beautiful--

(impact)

(screaming)

(narrator): The NTSB must now figure out

why a critical piece of safety equipment failed.

(crash)

- The traffic alerting system was installed...

in 1999.

One of the first in the country.

(narrator): They take a closer look

at the De Havilland Otter's traffic alerting system.

- It looks like FAA paid for it

as part of an experimental program.

- The Capstone Project that the FAA sponsored

was a program to reduce mid-air collision accidents in Alaska.

In 2015, the Otter got an upgrade from the FAA.

- What kind of upgrade?

- Take a look.

- They swapped out a Garmin transceiver for a RANGR 978.

- Yes.

And take a look at what wasn't

included in the upgrade.

(narrator): When the traffic system was upgraded on the Otter,

its alerting function was removed.

- The FAA considered the traffic alerting audio capability

to be classified as immature

and no longer part of the upgraded system.

That was a head scratcher for our team.

(narrator): But even if the Otter pilot

didn't receive an alert,

the Beaver pilot should have received one on his system.

In this part of the world,

alerting systems are neither mandated nor regulated.

Planes can have different systems or none at all.

- The Beaver pilot had been utilizing an iPad

that was using an application for navigating and understanding

where traffic would be in his surrounding area.

- The pilot paid for his own system.

- And so, he would have had a fully functional system,

including alerting capabilities.

- According to this, yes.

- I think it's clear the Beaver pilot was concerned about safety.

He had gone at his own expense and installed ADS-B equipment

in his airplane that was not required per regulation.

(narrator): Did the Beaver's system also fail

to alert the pilot?

Investigators use the ground station data

to recreate what the Beaver pilot would have seen and heard

in the cockpit leading up to the crash.

- The centre is the Beaver.

The Otter is at 3 miles out now.

(narrator): There is no alert warning of the approaching Otter.

- We're missing something.

Determining why neither of the traffic alerting systems

in the airplanes warned the pilots

about the impending collision was something that

we had to sort out in order to figure out

why the collision happened.

- Is that everything?

Thank you.

(narrator): With the Beaver's ADS-B system

destroyed in the crash,

the NTSB turns to the only evidence that remains:

salvaged parts of the Otter's traffic alerting system.

- Hey, check this out.

(mysterious music)

- It's turned off.

(narrator): A key component was not operating

at the time of the crash.

- That is odd.

- There was a critical piece of equipment onboard the Otter

called the GSL 71.

(narrator): The GSL 71 is a control panel

for the alerting system.

It broadcasts the plane's altitude

to aircraft and ground stations.

(Sauer): Let's see exactly how these components work.

(narrator): Investigators examine the role

of each component of the Otter's traffic systems,

to consider the consequences of having the GSL 71 turned off.

(sombre music)

- Well, this is not a simple set up.

- So, a surprising thing about the system on the Otter was that

it was a mixture of new and old parts.

Look at this.

- If the GSL 71 is off,

altitude information will not

be broadcast to other aircraft.

- If the Otter wasn't broadcasting,

then the Beaver would not have gotten an alert.

(narrator): Investigators get their biggest lead yet.

- Because the GSL 71 was off,

other aircraft had no idea

what altitude the Otter was currently operating at.

(impact)

Was that airplane above 'em,

below 'em, same altitude?

Unsure.

(dramatic music)

When was the last time the Otter

transmitted altitude data?

(soft investigative music)

(narrator): Investigators review

when the Taquan Air Otter

last broadcast its altitude to ground stations.

- April 29th.

- Um...

The last inspection and maintenance was uh...

April 30th.

- The day after its last broadcast.

(narrator): The team considers

whether the GSL 71 was turned off for maintenance

two weeks before the crash

and never turned on again.

(Sauer): We spoke to maintenance personnel,

but during the course of interviews,

we never really were able to completely understand

why the unit was in the off position.

(narrator): Since the Otter wasn't broadcasting its altitude,

the Beaver never received an alert.

Why didn't the Otter pilot check if he was broadcasting his altitude

on the day of the crash?

- I have some additional questions for you.

(soft piano music)

Were you aware that the control panel was off?

- No.

- Why not?

- I saw other aircraft on the display screen.

So that told me the system was working.

(narrator): Investigators discover that the pilot

didn't fully understand how

all the components of the traffic surveillance system worked.

- No conflict.

- We learned that there had been other pilots in the airplane

preceding the accident with the accident pilot

who apparently didn't catch that the GSL 71

was in the off position either.

I think on one of those flights,

he actually had the chief pilot of the company with him,

and the GSL 71 was still in the off position.

And we know that because the data wasn't streamed.

The pressure altitude wasn't streamed.

- Did you check to see if the GSL unit was "on"

during your preflight checklist?

- No, it wasn't a piece of equipment that I ever touched

or concerned myself with.

(narrator): They review the company's

preflight checklist with the Otter pilot

to understand why a crucial part of the alerting system

wasn't turned on.

- Radio set.

Altimeter set.

Fuel checked.

It's not on my preflight checklist.

(sighs)

- Okay.

Thank you.

(narrator): Investigators determine the Otter pilot

wouldn't have checked the status of the GSL 71.

(Bramble): In an airline environment,

something as critical as that

would definitely be on a checklist.

And so, the fact that it wasn't,

might lead him to think that it wasn't super critical

or it would just not have risen to the level of something that

he would pay attention to each and every time.

(melancholic music)

- What did you learn from the Otter pilot?

- He didn't know the unit was turned off.

It wasn't on his preflight checklist.

- You have to be so diligent at all times

when you're flying the aircraft, especially in a busy, busy area like that.

As good as the traffic systems can be, they can sometimes fail.

(narrator): The team now knows

why neither traffic system alerted the pilots.

- It still doesn't explain why the pilots didn't see each other

on a perfectly clear day.

See-and-avoid is the system by which pilots are taught

to avoid one another when air traffic control

is not providing positive separation.

It is considered a last line of defence

and it involves systematically scanning

different parts of the sky visible through the windscreen

to ensure that there aren't any other aircraft on a collision course.

- Okay, let's check out the pilots' field of view.

(narrator): NTSB Investigators consider exactly what the pilots

could see from the cockpits of their airplanes.

- Hmm...

So, the Beaver pilot would've been doing his scans,

looking left...

no problem.

Looking right...

hmm, there was a passenger in the front seat

restricting his view.

- And the Otter was to the right coming from behind.

- The passenger sitting in your seat

might have been able to see it.

But not the pilot.

- What about looking back through the cabin?

- Mmm...

I don't think so.

The windows are too small and passengers are in the way.

(sighs)

There's no way he could have seen the Otter

approaching from behind and to the right.

(Floyd): The Beaver has issues with visibility

because of the structural design of the airplane.

You have door posts, and window posts, and overhead structure,

etc., etc., that does obscure your view.

And, of course, in the old days,

that wasn't really a huge concern because, of course,

there was a lot less airplanes in the sky.

- The Otter pilot might have had

a perfect view to the left and straight ahead.

- Let's figure that out.

- So the Otter pilot said

he was lining up the waterfall to his right.

- So this was the pilot's field of view.

(narrator): Investigators consider what the Otter pilot

could see at the time of the crash.

- So let's assume that he was looking to his right,

say about 2 o'clock.

- Ah, but the pilot was adamant

that he was still doing his full visual scans,

left and right, up and down.

So what would he see if he looked to his left

towards the Beaver?

(narrator): Using a 3D scan of an Otter cockpit,

the team recreates the pilot's view

out the left windshield in the moments

before the collision.

- This is just minutes before the collision.

The Beaver is still 3 miles away,

roughly in this area of the windscreen.

(narrator): The Beaver is little more

than a speck on the horizon.

- It's hard to pick out the Beaver

against the dark mountains in the distance.

(Bramble): When two objects are converging,

there is little relative motion in a pilot's visual field

to attract a pilot's attention.

- Okay.

Got one 3 miles out, at 3 o'clock.

Opposite direction...

no conflict.

- The Beaver's an eighth mile away.

- I still don't see him.

(narrator): The window post, called an A-pillar,

obstructs the view of the Beaver.

- Okay, we're coming up on the moment of impact.

- The Beaver came out of nowhere.

- I didn't see it until impact.

(narrator): The Otter's ADS-B system doesn't have

the alerting capability to warn of the other plane.

And the pilot's view of it is obstructed.

- Okay, folks, in a few seconds,

we're gonna pass our famous--

(impact)

(Bramble): The animation was fascinating because

it showed how almost perfectly

the Beaver was obscured by the window post in the cockpit

of the Otter from the pilot's perspective.

And it wasn't until the last half-second or so that

it sort of blossomed from behind the post and became a red flash.

(narrator): But they can't be completely certain.

- It's hard to know for sure.

His perspective is gonna change,

depending on where his seat is set, and where his head is.

(narrator): Investigators need more information.

(Sauer): We can change sight lines,

we can adjust angles,

we can adjust views,

but we do not have the ability to say that that was, in fact,

the pilot's position at any point in time

during that flight.

(narrator): The team performs a study

using 27 different eye positions

to evaluate how the A-pillar

would have blocked the Beaver from the Otter pilot's view.

- The Beaver is mostly hidden.

- Except for here.

It's hard to be 100% certain

without knowing the pilot's exact seat position.

(investigative music)

- What about the cameras that we recovered from the wreckage?

Maybe there's something on them.

- I'll check on it.

Based on it being an air-tour operation being in 2019,

fortunately, we were able to locate

quite a bit of still imagery and video.

- Okay, let's see what we've got.

(narrator): After several weeks of painstaking work,

investigators review images taken by the Otter passengers.

(mysterious music)

- No. There's nothing here.

(narrator): There are no pictures

taken near the time of the collision.

- Let's check out the photos taken from the Beaver.

Whoa.

(narrator): They find a photo of the Otter

taken by a passenger in the Beaver.

- It was eerie and disturbing

to see the photos taken by the passengers.

Let's take a closer look.

(narrator): The photo of the approaching Otter

was taken seconds before impact.

(dramatic music)

(plane buzzing)

(Bramble): It was a moving experience.

You knew it was gonna be the last moments for some of those people.

- Uh, zoom in.

(narrator): But can it answer the question of whether

the Otter pilot could see the Beaver?

- I can see into the Otter cockpit.

(narrator): It's the break the investigators needed.

- Uh, try to zoom in a little bit more.

(narrator): The photo captures the Otter's exact position.

- The A-pillar is blocking the pilot's head.

- If we can't see the Otter pilot's head

from this perspective,

he wouldn't have seen the Beaver.

(narrator): Investigators are now certain

that for almost three minutes before the collision,

the Otter's windshield structure

blocked the pilot's view of the approaching Beaver.

(Sauer): It was crucial for us to understand that

at that point, the Otter pilot had very limited chance

of avoiding that collision

due to his sight being obscured

by that aircraft structure.

(narrator): Investigators now understand

why the Mountain Air Beaver

and the Taquan Air Otter collided.

- Okay, folks, in a few seconds,

we're gonna pass our famous--

(impact)

(narrator): Neither pilot could see nor be alerted

to how close their aircraft were to each other.

(Otter pilot): Hang on, everyone!

Brace for impact!

(crash)

(Floyd): You just can't afford

not to have a traffic system.

When it's so busy as that, in terrain like that,

when the pilot is so darned busy,

he needs all the help he can get.

(narrator): The NTSB's final report

highlights the limitation of see-and-avoid for pilots

and recommends new rules for preventing the downgrading

or disabling of traffic-alerting systems.

(Bramble): This accident in a nutshell,

to me, is about the rolling back of safety protections

without anybody taking a critical look at

what they were doing.

(soft piano music)

(narrator): The NTSB recommends regulations

requiring mandatory air traffic alerting

for air tour operators in high-traffic areas.

(Sauer): I have worked a number of mid-air collisions

during my career here at the NTSB,

and this accident was very preventable.

There are limitations, as all of us all well know,

with the concept of see-and-avoid,

and the technology that exists today

should be in these aircraft to help reduce

these numbers of collisions that take place.

(♪♪)

Subtitling: difuze