All language subtitles for Historys.Greatest.Mysteries.S05E10.The.Hindenburg.Disaster.1080p.HULU.WEB-DL.AAC2.0.H264-WhiteHat_track3_[eng]

- Tonight, a historic
catastrophe captured on film.

- [Broadcaster] It's
burst into flames.

Oh, my!

Oh, the humanity!

- Of the 97 people on
board the Hindenburg,

13 passengers, 22 crew,
and one ground crew person

all perished in this event.

- The Hindenburg Disaster,

in many ways, it was
the first viral video.

- For decades, experts believed

they knew what
caused the disaster,

that leaking hydrogen ignited,

causing the airship
to burst into flames.

But there may be
more to this story.

- Eyewitness testimony says that

they saw orange and red flames,

but hydrogen, when it burns,
it burns a light blue.

- Some people on the ground
report having heard popping

inside the aircraft
during that last turn,

like something inside
of it went wrong.

- Now, we'll explore
the top theories

behind this historic tragedy.

- Basically, the Hindenburg
is flying with bandages on.

- He gets actual fabric
from the Hindenburg,

and poof.

It goes up in flames.

- What really caused
the Hindenburg Disaster?

(dramatic music)

- [Laurence] Frankfurt,
Germany, May 3rd, 1937.

The world's largest
aircraft, the Hindenburg,

prepares to depart
for New Jersey.

The airship's tanks are full
of hydrogen and nitrogen,

fueling its 11th
transatlantic flight

to the United States.

- The Hindenburg is
a derigable aircraft

that's filled with gas and
that makes it lighter than air,

so it can basically float.

- Hindenburg provided something

that no other type of
aircraft could provide.

Three day passage from
Europe to the United States

in great luxury.

- [Laurence] At 7:16pm,

the Hindenberg takes off
for Lake Hurst, New Jersey.

More than 10 stories tall,
stretching 804 feet long,

the Hindenburg is roughly
the same size as the Titanic.

Unlike a hot air balloon,

the Hindenburg is
a rigid airship

constructed with a metal frame.

- It's filled with 16
cells of hydrogen gas,

which is a gas that's
lighter than air,

which makes it buoyant.

It floats without
needing to be lifted up

by any sort of wings.

- The ship has a
triangular structure

through the very center
that runs all the way.

That's actually what the
crew would walk across.

And around that are
these metal frameworks

like the ribs of a barrel,

and outside of that
is an outer coverage,

seven acres of
aeronautical cloth

that has been painted
and carefully sealed

so that it is both waterproof

but also sturdy
from the elements.

- Aluminum powder in the varnish

is what gave the Hindenburg
its silver color,

but it also served the purpose
of reflecting the sunlight

so that the hydrogen
gas did not get heated,

inflate, and burst.

- [Laurence] Beyond its
technical achievements,

the Hindenburg is a
floating representative

of a sinister government.

- The swastikas
emblazoned on the tail

were the national flag
of Germany at the time.

So basically, the Hindenburg
served as a flying billboard

for the Nazi
government in Germany.

- [Soldiers] Sieg
Heil! Sieg Heil!

- [Laurence] Thanks
to recent upgrades,

the Hindenburg now
carries 72 passengers

and almost as many crew.

A one-way ticket costs roughly
$8,500 in today's money.

- The Hindenburg was set
up for luxurious travel.

There were two decks

that included a
dining room, washrooms,

a full electric kitchen,
and even a smoking lounge.

They also had a grand piano

that had been
constructed of aluminum

and covered in pigskin.

- For the most part,

the Hindenburg would
travel about 650 feet

above land or sea.

Captains were very conscious
of the passenger experience

and they would actually
lower the altitude

to allow them to
see amazing sights

that no one in
humanity ever had,

like icebergs from
above, floating by.

- [Laurence] After a four year
long construction process,

work on the Hindenburg
is completed in 1936,

and that spring, it begins its
first international flights

to the United States and Brazil.

- It was spectacularly
successful in 1936.

It went back and forth
across the Atlantic,

both the North Atlantic
and the South Atlantic,

and so they entered
the 1937 season

with so much pressure
on them to make this

first North American
flight of 1937 a success.

- [Laurence] On May 6th, 1937,

after a nearly
three day journey,

the Hindenburg
reaches American soil.

- As the Hindenburg is
heading for its destination,

Lakehurst, New Jersey,

there are storms ahead of it,

and so the Hindenburg can't
land when it's supposed to.

It spends hours waiting
for the storms to clear up,

and there are film
crews and radio crews

waiting to see this
amazing sight.

- What the ship
is supposed to do

is approach a structure
known as a mooring mast,

and once there, drop
the landing ropes.

At that point, the
ship drops its ballast

and then a crew of
about 200 burly men

grab a hold of those ropes,
attach them the winches,

and then start bringing
it down to the ground.

- [Laurence] Then at
7:25pm, disaster strikes.

- As the ship is landing,

the tail is getting closer
and closer to the ground

and they try to release hydrogen

in an effort to bring that
ship back into level.

- Unfortunately, it's
just not working.

The tail continues to
fall below the bow.

And then suddenly,
an explosion occurs.

- [Broadcaster] Oh, my!

It's burst into flames.

400, 500 feet into the sky.

(explosion booming)

This is terrible.

This is the worst of the worst
catastrophes in the world.

The smoke and the flames now.

(dramatic music)
(explosion booming)

Oh, the humanity!

- Of the 97 people
onboard the Hindenburg,

13 passengers, 22 crew,
and one ground crew person

all perished in this event.

- It's kind of
insane to think that

people started
jumping from the ship

in order to save themselves.

Some of them actually
died because of the fall.

- Miraculously, about two
thirds of the people on

actually lived
through this disaster.

- [Laurence] Investigators
immediately suspect

that sabotage is involved.

- Given that it
is one of the most

visible spectacles on Earth and
has a giant swastika on it,

naturally, that would seem
to be the perfect target

to take down the Nazis.

So everyone immediately thought

there must have been a saboteur.

(tense music)

(clock ticking)

- Because the Hindenburg was
used as a Nazi propaganda tool,

it's a natural target
for anti-Nazi activists.

The Hindenburg senior captain
Ernst Lehmann reports that

just before leaving Germany,

they received a warning
that there was a threat

to bomb the Hindenburg when
it was over American soil.

- Hugo Eckener was the
head of the company

that built the aircraft, and
he would ultimately indicate

that he received threats,
directly, that the aircraft

should not proceed to
Lakehurst, New Jersey

because something bad
would happen there.

- Given this warning,
the German security,

before taking off, was
extremely stringent.

They went through the mail,
they went through the luggage,

and nothing was found, but
this was early days of security

and something may
have slipped through.

- Charles Rosendahl, a
commander of NAS Lakehurst,

suggested to the FBI

that they should
investigate a passenger

who had a dog in the
cargo compartment

right around cell six,

and he had been visiting the dog

unaccompanied by a member
of the ship's crew.

- [Laurence] The man with
the dog is soon identified

as passenger Joseph Späh.

- Joseph Späh is born in Germany

and then immigrates to the
United States as a young boy.

He's an entertainer in the
tradition of vaudeville.

He does monologues, standup,

he's also an acrobat
and a contortionist.

And he's been on
a tour in Germany

and now he's taken the
Hindenburg back home.

During the latter part
of his German tour,

he purchases an expensive
German Shepherd puppy named Ulla

to use in his act,

and he takes Ulla back
with him to America.

And so Ulla is in a kennel

and is kept in the cargo
hold of the Hindenburg.

- [Laurence] Crew members
report that during the flight,

Späh insists on feeding
the dog himself.

- The passengers aren't allowed

to simply wander to the
cargo bay on their own,

that's usually
what the crew does,

so this behavior gets
the crew's attention.

- Several of the
stores report that

Späh was acting strangely.

In particular, when
the Hindenburg

was delayed for several hours
due to the thunderstorms,

he had this urgency to land.

- He was getting impatient
when the Hindenburg

was not quite landing on time,

which if you had planted a
bomb that, say, had a timer,

would be a reasonable
thing to be doing.

- [Laurence] As
investigators learn more

about Späh's background,
suspicions deepen.

- In addition to having visited

the inside of the
hull of the ship

without being accompanied,

Joseph Späh is a
professional acrobat.

He easily could have climbed
around the rigging of the ship.

- So because of his
acrobat abilities,

he could have made
his way outside

of where he was supposed to be,

worked his way to the
tail of the aircraft,

climbed up a ladder
all the way to the top,

and placed a time bomb
somewhere on the airframe

between two hydrogen bags,

and that explosion could have
brought the aircraft down.

- [Laurence] But even if Späh
had the means to plant a bomb,

what was his motive?

- Although by this point, Späh
is officially an American,

he is German by birth,
and so maybe he thinks

that the rise of the
Third Reich in Germany

is bad for his homeland.

In fact, some of the
crew members on the ship

recall Späh making
anti-Nazi jokes on board.

- He's investigated by
the FBI, but they find

that there's absolutely
no evidence suggesting

that he planted a
bomb on the aircraft.

- The truth is, no one that
looked at the wreckage

ever found any
evidence of a bomb

or of any sabotage
of the Hindenburg.

Some people who look
at this feel that

the reason why Captain Pruss

and other bigwigs
from the company

were pushing this
idea of a saboteur

is because they wanted
to free themselves

from any responsibility
for this horrible tragedy.

- [Laurence] As
investigators search

for the explosions caused,
they turned to another clue.

Weather.

- There were storms
all over the area

of Lakehurst, New
Jersey that day.

And at the time of the
Hindenburg landing,

winds were gusting
at 30 miles per hour,

there was lightning,
it was chaos.

- There's communication
from the ground command

and the captain on the ship.

The commander on the ground,
Commander Rosendahl,

he says the weather
is too strong,

the thunderstorms are too much
for the airship to come in.

And so the Hindenburg has to
circle around a number of times

because it's three
hours of storms.

(thunder cracking)

- Just because the
storm has moved out,

we're seeing cells
in the distance,

even upwards of
10 plus miles away

doesn't mean it's
not gonna impact.

But people may have
let their guard down,

thinking, okay, that
activity has passed.

But that activity,
it's still lingering.

- At the time, the
New York Daily News

reports a number of theories

for what brought
down the Hindenburg.

The leading theory, lightning.

(thunder cracking)

(tense music)

- [Laurence] A typical lightning
bolt carries 300 million volts

and can reach temperatures of up
to 50,000 degrees Fahrenheit.

- There's more than enough
energy when it comes

to lightning to
cause destruction.

We see that with forest fires

and even when it
strikes tall buildings.

- [Laurence] And
there's precedent

for lightning
striking a Zeppelin.

- In 1917, a Zeppelin
was brought down

and 23 people were killed

when it was struck by
lightning over the Baltic Sea.

Another incident
occurred in 1923

when an airship called Dixmude
was struck by lightning.

It exploded in midair,

killing all 50 people on board.

- [Laurence] But while
the weather conditions

improved enough in
Lakehurst to begin landing,

some believe it's possible
that the Hindenburg is struck

by a rare phenomenon
called positive lightning,

which triggered the
terrifying explosion.

(thunder cracking)

- During the storm, there's
extreme electrical movement.

Negative charges build up
on the bottom of the clouds,

positive charges build up
on the top of the clouds.

- This so-called
positive lightning

is a connection
between the ground

and the upper
reaches of the cloud

rather than the bottom
reaches of the cloud.

So it has to travel a
much greater distance,

and because of this,
the lightning strikes

from positive lightning

can be up to 10 times stronger
than negative lightning.

- These positive
lightning strikes

can happen 20, 30
miles from a storm,

so you can be without a
storm in your general area

and a bolt can come
out of the blue.

- [Laurence] But those
who know the Hindenburg

question whether it can be
taken down by lightning.

- The captain of the
Hindenburg, Max Pruss,

told investigators
that he'd flown

through lightning storms
in the Hindenburg

several times before and
the ship had been hit.

But he said the
lightning strikes

would basically just
cause some burn marks

on the outside of
the skin of the ship,

but there was no further damage,

so they were no problem as
far as he was concerned.

- [Laurence] Witnesses
on the ground

did not see lightning
as a factor.

- There were many witnesses,

a thousand people on the ground
looking up at the Hindenburg,

and nobody saw a
bolt of lightning.

- [Laurence] But that doesn't
mean the stormy weather

didn't play a role.

- The Germans knew a fair amount

about how to safely
handle hydrogen,

and one of the
biggest rules of all

was you do not land a hydrogen
airship in a thunderstorm.

But they felt under
pressure to land,

and so they basically ignored

one of the oldest rules
in their own book.

- There was a bolt
out of the blue,

a big flash that
happened in a distance.

It came at the top of the cloud

and you might not
necessarily see that.

So it's gonna strike
about 20 to 30 miles away,

it's gonna be very quick.

So potentially, they
may have just missed it

because it happened that fast.

- [Laurence] In the wake
of the Hindenburg disaster,

both the American and
German governments

conduct investigations

into the cause of the
airship's explosion.

- So, the investigation
interviews

witnesses on the ground,

it goes through
all of the wreckage

that's in place
there at Lakehurst,

and it takes into account every
piece of possible evidence

that can be assembled

to put together a picture of
what happened to this aircraft.

- [Laurence] In August 1937,

three months after the incident,

the US government
releases its report.

The official German report
is issued five months later.

Both come to
similar conclusions.

- The Hindenburg is constantly
venting hydrogen gas

to help with steering,
to help slow it down,

and it is this hydrogen gas
that the investigators find

that is responsible for
the Hindenburg burning.

- [Laurence] As to what
actually sparked that explosion,

neither report comes to
a definitive conclusion,

but many scientists
share the same theory.

- When you have a
highly flammable mixture

of hydrogen and oxygen,
all you need is a spark.

(flames roaring)

(tense music)

- [Laurence] On May 6th, 1937,

as the Hindenburg flies
from New York City

south to New Jersey, the
ship faces troubling weather.

- Around 6:00pm, there's heavy
rain falling in Lakehurst

and lightning
strikes were reported

throughout much of the day.

- Due to the storms, there's
so much electrical activity

that local rubber
factories are shutting down

because they have
powdered rubber

and powdered rubber
is combustible.

- Like hydrogen, rubber
dust is incredibly flammable

and explosive.

So if it were to
come into contact

with a spark from
a lightning strike

or some other
atmospheric electricity,

that would be a bad situation.

- By the time the
Hindenburg is ready to land

in Lakehurst, New Jersey,
it's already been pushing

through a high electric
field for hours

- [Laurence] In the
wrong conditions,

the Hindenburg's outer covering
can act as a conductor.

- The German investigators
determined that

the particular formula used
for the dope for the fabric,

including the powdered aluminum,

creates a substance
that has the ability

to hold a charge
when it gets wet

and it was wet that day
because of the rain.

- So what's happening
to the Hindenburg

is very similar to what happens

when you rub your feet on the
carpet while wearing socks.

It builds up an electric charge.

Then if you go and touch
an electrical conductor

like a doorknob
or a light switch,

that charge that you built
up wants to go somewhere

and that's why you get this zap.

It's an electrical
static charge.

- [Laurence] For the
Hindenburg to go up in flames,

that spark needs to
come into contact

with something flammable.

- Now, Hindenburg is
traveling with 16 bladders

full of hydrogen,

which is extremely flammable.

We know that the
aircraft probably

had a hydrogen leak in it

because as it's approaching
the mooring mast,

it's tail heavy,
nose high, tail down.

So they begin dumping ballast

from the after part
of the aircraft

to potentially
right the aircraft.

What the crew is doing is

treating a symptom,
not the illness,

and the illness was
there's a hydrogen leak

somewhere in the
tail of the aircraft.

- [Laurence] At 7:21,

the Hindenburg arrives
at its mooring mast

and prepares to land.

- The Hindenburg has
just gone through a storm

and it's accumulated
a lot of charge,

both on the skin
and the metal frame.

So as the Hindenburg
is coming into land,

it drops its landing lines

which are attached
to the metal frame.

So the metal frame is
grounded through those lines

and the excess charge
on the metal frame

can move into the ground,

meaning there's not as much
of a concentration of charge

on the metal frame.

So the skin, with a high
concentration of charge,

will want to go to that
lower concentration

and you get a spark.

- So if a spark is generated

and it comes in contact
with free floating hydrogen,

(flames hissing)

there are gonna be
flames and an explosion.

- [Laurence] Some critics
challenge this theory.

- In particular,
it's the timing.

The fire does not
ignite at the moment

the mooring ropes are dropped.

If the idea is the ropes
complete the circuit

and that's what
generates the spark,

then we would expect
to see the flames

at the moment the
ropes are dropped.

Instead, the explosion
happens four minutes later,

which could indicate
a different trigger.

(explosions booming)

- In the months after
the Hindenburg goes down,

US and German investigators
agree on a key fact,

bad weather contributed to
the airship's explosion.

But could something
other than mother nature

have caused this
tragic accident?

On May 3rd, 1937,

as the Hindenburg departs
for Lakehurst, New Jersey,

the Zeppelin is already
a worldwide phenomenon.

- The Hindenburg had had
an amazing year in 1936.

It had done seven round
trips to Rio de Janeiro

and 10 round trips to America.

- So the Hindenburg's
maiden season

was really quite successful.

If you think about it, 200,000
miles, nearly 3,000 passengers,

with virtually no problem.

The record for the first
year was very strong.

- The Hindenburg was looking
to do a very rapid turnaround

and head back to Europe

for the coronation
of King Georgia VI.

So because of that, there's
intense pressure on a captain

to get this thing on the ground.

- [Laurence] Captain Max Pruss
prides himself on punctuality,

but by the time the Hindenburg
reaches Lakehurst, New Jersey

on the evening of May 6th,

the airship is already more
than half a day behind schedule.

- There were strong
headwinds over the Atlantic

and now, weather and storms
in the northeast of America

is even pushing him
further behind schedule.

It was horrible weather and
so, anxious to land quickly,

Pruss decides to modify
his final approach.

- He's no longer able
to go in a straight line

because the wind has shifted,

and so in order to put the
bow of the ship into the wind,

he needs to make a turn to
starboard, or turn to right.

- The pilot is a
little bit further

out of position
than he wants to be,

and so the aircraft moves in

faster than it would
typically approach,

and then it carries out
this large swinging maneuver

to burn off air speed
to reduce that momentum

as it approaches
the mooring mast.

So it comes sort of hauling
in as fast as it possibly can,

which is not a breakneck speed,

but for that aircraft, it is.

- Some people have
expressed a thought

that this final turn may
have overstressed the ship.

- Some people on the ground
report having heard popping

inside the aircraft
during that last turn,

like something inside
of it went wrong.

- [Laurence] As the Hindenburg
moves into its final position,

all hell breaks loose.

(tense music)

- It's believed that the popping

that some people on the ground
heard during that last turn

may have been the
sound of the wiring

that secured the rigid
internal frame of the aircraft.

Maybe one of the wires snapped.

And that would've
explained the popping noise

that was heard by some
people on the ground

and that that last
turn had caused

that high tension
cabling to snap

and that it was somewhere
in the tail section

of the aircraft.

- If a bracing wire snaps,
you now have this jagged wire

that's flailing about on
the interior of the ship

near some of the gas cells.

So a rusty, jagged wire
could then flail about,

hit one of the gas cells,
and cause a rip in it.

That rip then allows hydrogen

to leak out into the body of
the ship and mix with air.

- [Laurence] With so much
transatlantic travel,

the Hindenburg may have
experienced wear and tear.

- You have to wonder,

the Hindenburg was
constantly crossing the sea,

exposed to salty sea air,

which can add corrosion,

so that could have compromised
its internal structure somehow.

- The bracing wires
were made out of steel.

The aluminum framework was
highly corrosive resistant,

but steel can corrode.

So over time, the Hindenburg
is accumulating humidity

and that moisture can
lead to corrosion,

which can also weaken
the bracing wires.

- So if there was weakened metal

that was anywhere
within the ship,

once the captain started to
take those really sharp turns,

that could have
added more stress

on the framework
of the aircraft.

One of the broken wires could
have actually punctured a hole,

then the hydrogen cells,

that would've released
more of that hydrogen.

Hydrogen mixed with air

creates a very combustible
and flammable environment.

- At this point, all
you need is a spark.

Boom, the Hindenburg
goes up in flames.

But the missing
piece from this is

what caused a spark
in the first place?

- [Laurence] Observers
on the ground say

they saw signs of a
different structural flaw.

- There were some
witnesses on the ground

who said right
before the explosion,

they could see parts
of the outer covering

flapping in the wind
on top of the ship.

- [Laurence] In 2020, some
80 years after the disaster,

author Michael McCarthy
discloses new evidence

he uncovered in German
archives that suggest

not only that this flaw
contributed to the crash,

but that the Zeppelin company
was well aware of the danger.

(tense music)

- The Hindenburg, it turns out,
had a hidden structural flaw

that created a
destructive rattling.

The problem was the outer
cover, the aeronautical cloth,

which is supposed to
protect the vehicle,

actually was
rattling excessively.

And vibration bedevils
all kinds of machinery.

Vibration is the thing

that makes things break
down and fall apart,

and this is what was
happening on the Hindenburg.

- They found that this flapping

was causing the metal ribbing
to rub up against the cells

that held the hydrogen gas,

basically chafing and thinning.

- Germans learned about
this several months

before the tragedy and
they tried to fix it.

So what they decide to
do is tie off with cord

all the metal crossovers

so that they reduce
the amount of pressure

onto the gas bags,

and then they take
strips of tape

that are one and
a half inches wide

and they put 'em wherever

the gas bags had
been abraded before

as a protective measure,

and they resow the thing back
together, and off it goes.

So basically, the Hindenburg
is flying in its second season

with bandages on.

- There's a belief that possibly
some of that patching work

ultimately broke loose during

the bad weather that
was encountering

over Ocean County,
New Jersey that day,

and that maybe some
of that flapping skin

was broken loose also by

whatever structure inside the
aircraft may have broken loose

during the high turns

that immediately proceeded
its final approach

to the mooring mast.

- [Laurence] Proving this
theory is a challenge.

- The hydrogen fire that
the Hindenburg encountered

was so severe, so strong,

that the physical evidence
is virtually non-existent.

There are pieces,
there are shards,

there are little things
in museums and so forth,

but the physical
evidence was virtually

completely destroyed.

- [Laurence] For decades,
most scholars agree

the Hindenburg was brought down
by an ignition of hydrogen.

Given how combustible
that gas is,

it seems like a
foregone conclusion.

Then in 1996,

a NASA scientist
named Addison Bain

proposes a
controversial new theory

that experts have targeted
the wrong part of the ship.

- For years, the Hindenburg
was frequently used

as the example for the dangers
of using hydrogen as a fuel.

But while Bain was
researching hydrogen

for his own rocket booster,
he began to think that maybe

hydrogen was falsely accused.

- [Laurence] Bain says his
first clue comes from the color

of the Hindenburg's flames.

- Eyewitness testimony says that

they saw orange and red flames.

But hydrogen, when it burns,
it burns a light blue.

So maybe it wasn't the
hydrogen that it was burning.

- [Laurence] Bain also says

that if there was
a hydrogen leak,

it would've left
a telltale sign.

- Shortly before the
Hindenburg disaster,

there was a gas explosion
in the United States

that destroyed a school
and killed 300 people.

So the Germans were well
aware of the dangers

of using hydrogen
in these aircraft.

So to deal with that,

the Germans added an
advanced early warning,

which had an odor
component to it,

and it smelled like garlic.

- We know there was crew

stationed near the
back of the aircraft,

but none of them reported
smelling garlic or the gas

before the disaster occurred.

Another thing that Bain notices

is that once the
tail of the aircraft

was engulfed in flames,
it still remained level.

So to him, that meant
that it was still buoyant

and hydrogen gas bags
were still intact.

- So Bain comes up with a theory

that the plasticized lacquer
on the skin of the Hindenburg

is much more dangerous than
the hydrogen inside of it

because it contains elements
that, when combined,

are highly combustible
on their own.

(tense music)

- [Laurence] The skin of the
Hindenburg is a cotton canvas

painted over with a substance
known as aircraft dope.

- Aircraft dope is
a type of lacquer

that is used on a cloth
covered airship of some sort,

stiffens the fabric,

and it acts as a barrier against
water, wind, and objects.

- [Laurence] The materials in
the lacquer contain iron oxide

and powdered aluminum,

elements used today
in rocket boosters.

Bain believes this ultimately
dooms the Hindenburg.

- It was common practice

for lacquering
airships at the time.

So imagine that.

Take the stuff from a
solid rocket booster

and paint it all
over your airship.

- [Laurence] Bain puts
his theory to the test.

- He believes that the skin
would burn up just as quickly

as rocket fuel would,

so he gets actual fabric
from the Hindenburg

with that plasticized lacquer
which he thinks is combustible,

and he puts a very high
voltage, 30,000 volts

across that fabric, and poof.

It goes up in flames.

- Bain believes that this
test proves his theory,

and that is that there
was an electrical arc

that didn't set off hydrogen,

but instead set off the aluminum
powder and the iron oxide

that make up the
skin of the aircraft.

- When Bain reports his
findings, he says to the press,

"The moral of the story is,

don't paint your aircraft
with rocket fuel."

- [Laurence] But Bain's theory

leaves some
questions unanswered.

- It's very difficult
to conclude anything

from the color of the flames,

not only because the witness
testimony is unclear,

but more importantly,

but Hindenburg was not
a pure hydrogen flame.

It was a bunch of stuff.

You had a ship that
had fabric covering,

it had metal, it
had steel wires,

it had all sorts of
combustible materials

burning all at the same time

that contributed to whatever
color that flame was.

- What's interesting about
the explosive paint theory

is that the photographs
we see of the explosion

don't show the canvas
going up in flames.

We see internal
flames in the ship.

Also looking at how it burned,

there's lines that run along

the locations of
those hydrogen cells,

which in the images,

it shows that the hydrogen
was actually burning

and not the canvas itself.

- Anytime someone has
a sensational theory,

it naturally invites challenges.

And one researcher actually
looked at claims around paint,

and what he found was that
there was no possible way

that a spark could physically
ignite that dope material.

- They've done experiments
using the chemical compounds

that were on the canvas

to estimate how long it would
take for the canvas to burn,

and the estimate
is about 40 hours,

not 34 seconds.

- [Laurence] In 2000,

an 81-year-old witness to
the Hindenburg disaster

comes forward to tell his story
publicly for the first time.

He was just 17 when the
Zeppelin went up in flames.

- Bobby Rutan was a child
of one of the Navy personnel

at the Lakehurst Navy Base

and he lived about 3,000 feet
from the site of the disaster.

- He knew a lot about airships

because his father had
died a few years earlier

in a disaster with another
airship, the USS Akron.

- As a teenager, Bobby
hung out in the hangers,

he sold souvenirs and
answered questions

from tourists who came
to view the zeppelins.

- [Laurence] On the
evening of May 6th, 1937,

Bobby is on the base and goes
out to watch the landing.

- As the Hindenburg
is coming in,

Bobby thinks he smells
some diesel fuel,

and then he hears what he
thinks is an engine backfire,

which makes him think

that the fire and the disaster
that he subsequently sees

is caused by the backfire
of one of the engines.

(tense music)

Hydrogen isn't the
only combustible fluid

that's on the Hindenburg.

It also burns around 300
pounds of diesel fuel

through the engines.

Diesel fuel is highly flammable,

so if it meets with
something that's hot,

say an engine block,

then the diesel fuel
itself can combust.

- [Laurence] There had
been recent trouble

with one of the
airship's engines.

- A fuel pump on one
of the diesel engines

was replaced in flight,

but there's always
the possibility that

the installation of the new pump

might have been
completed incorrectly

and that there might
still have been

a problem with that engine.

- So, some have suggested

that replacement caused
the engine to backfire

and result in the
ignition for an explosion.

- [Laurence] As the
investigation gets underway,

Bobby immediately comes forward.

- Bobby told Charles Rosendahl,

who was the commander of
the Lakehurst Air Base,

that he smelled this fuel

and that the backfire
could've ignited it,

leading to the explosion.

- Commander Rosendahl
is having none of it.

He doesn't want to
muddle the story

because he believes
that it's sabotage,

and he doesn't want
Bobby saying to others

that there could be a
cause that has to do

with say, the engine.

He even tells Bobby's
stepfather that this

should not be information
that's spread around.

- So why would Rosendahl do it?

He has two reasons.

One, he was the
one who suggested

that the airship
come in when it did

after circling for
at least three hours,

and of course, it
turned into a disaster.

So he has some personal
responsibility there.

But it's more than that.

He is a real protector
and an evangelist

for this form of flying.

Even when the technology
starts to fade

in terms of people's
enthusiasm for it

and the public's
enthusiasm for it,

he still continues to
be its main cheerleader.

So he doesn't want
this information out.

- [Laurence] Bobby stays
silent for decades.

He insists everything he
says he saw that day is true.

- Years later, when asked
if the fuel that he smelled

could have come
from another source,

Bobby Rutan answers,
"Absolutely not."

There is nothing on the base

that it could have
given off that smell.

There's only blueberry
fields on one side

and sand on the other.

- [Laurence] In 2007, the last
surviving ground crew member

corroborates Bobby's account.

- Robert Buchanan
had been on the job

in 1936 when the
Hindenburg landed.

Buchanan recalls that as
the airship is landing,

the pilot does a hard maneuver
to slow the airship's descent.

- Robert Buchanan corroborates
Bobby Rutan's account,

saying that he could see sparks

after the pilot completed
that hard right-hand turn.

- He also heard the
backfiring engine

and even saw sparks
coming out of the engine.

- Buchanan feels intense heat,
and he runs for the trees

It's so hot, he doesn't
think he's gonna make it,

but once he makes the tree line,

he looks back and he
sees flames erupting.

- [Laurence] It's a
dramatic account,

but not everyone is convinced.

These decades-old
memories add up.

- The Commerce Department
interviewed hundreds of people,

not once did anyone suggest that
there was a fire or a spark

that began on the engines,
which were at the bottom.

And remember, fire
was at the very top.

It was a sawtooth flame
right along the tail,

nowhere near the engine,

so the distance
is simply too far.

- The other problem
with the idea

that the fire was started by
one of Hindenburg's engines

is that it is not credible

that anyone who was
located in the area

where the general public was
allowed to watch the landing

could possibly have
smelled anything

that was leaking or dripping

from an airship that was
almost half a mile away.

In addition to that, the
general public was in an area

that was right next to
the aircraft hanger,

which was filled with aircraft

that were all
powered by gasoline.

- [Laurence] The
Hindenburg's fatal flight

remains a topic of
enduring fascination.

- There was no footage
of how it started.

The rubble was
completely demolished.

We don't have the evidence
to make a final conclusion

and so, we may never
know what happened.

(flames roaring)

- Whatever triggered
the explosion,

it didn't just spell
doom for the Hindenburg,

but for the entire
rigid airship industry.

Two years after the disaster,

transatlantic airplane
passenger service begins.

A new age of international
travel is born

and the Zeppelin
fades into memory.

I'm Laurence Fishburne.

Thank you for watching
"History's Greatest Mysteries."

(dramatic music)