Original subtitles

Helios 522, do you read?

High above Athens,

fighter jets track a 737 as it circles the city.

522, do you read? Over.

There's no answer from the passenger plane,

but there is someone at the controls.

More than a hundred people are on board.

Everybody's mind was going to hijack or terrorist.

There is one person moving in the cockpit.

Repeat there is one person...

What happened to the crew and passengers?

522, do you read? Over.

And who is flying the plane?

Helios 522, do you read? Over.

Early morning, August the 14th, 2005.

The cabin crew of Helios Airways flight 522 are preparing

for their trip from the island of Cyprus to Athens, Greece.

Sure is a beautiful day.

Maybe I shouldn't have come in.

Andreas Prodromou is twenty-five.

He isn't supposed to be working today

but he's taken the flight to spend some time

with his girlfriend, who also works for Helios.

It's the sort of day I'd like to be out flying.

You will Andreas.

Prodromou is a flight attendant now

but he has bigger plans.

One day he wants to fly for Helios.

His dream was to become a professional pilot.

Personally, I wanted him to stay in the family business.

We often talked about this. We've got company.

Stay warm in the back. See you in Athens.

In the cockpit, the flight crew is occupied

with the daily routine of preparing their jet for takeoff.

It's bright today.

09 Captain Hans Merten is an East German,

a contract pilot hired by Helios for the busy holiday season.

Are you almost through? Pardon?

Are you almost done? Nearly.

His co-pilot is from Cyprus.

Pambos Charalambous has been working

exclusively for Helios for the last five years.

Before beginning any flight, crews are required to perform

dozens of checks on various pieces of onboard equipment.

It's a routine but necessary procedure.

Doors closed.

Sorry. Could you store trays and put your seat back.

Helios is a charter airline,

with low cost fares to Greece.

It's a summer weekend, and the plane is filled with families.

In all, there are 1-hundred and fifteen passengers

on the morning flight.

If you need any more help, let me know.

We're just about to take off.

They are low fare, no thrills.

Uh they don't even serve you refreshments

during small sorts of flights.

But they often another possibility

for the budget minded traveler.

Paros Demetriou and Maria Rikkou

are traveling to the Greek island of Patros.

They've just got engaged.

They booked, they booked this holiday a month,

or more than a month ago.

It was like a honeymoon for them.

Flight attendants, please take your seats.

Prepare for takeoff.

Just a few minutes after nine in the morning,

Helios Airways flight 522 lifts off into the bright sunshine.

Nicosia area control, this is Helios 522.

Request cruising at 3-4-0.

Helios 522, you are cleared to climb to 3-4-0.

Have a good day.

Set 3-4-0. 3-4-0.

Minutes into the flight,

the plane is still climbing towards its cruising altitude.

Suddenly, an alarm blares in the cockpit.

What is it?

The takeoff config warning?

The flight crew is confused.

The takeoff configuration alarm

normally only sounds on the ground.

It tells pilots their jet isn't ready for takeoff.

The crew doesn't know why it's sounding now.

Uncertain what the problem is, the captain radios

the Helios operations center at Larnaka Airport back in Cyprus.

Operations, this is flight 522. Over.

Flight 522, what can I do for you?

We have a takeoff config warning on.

Pardon?

Our takeoff config warning is on.

I'm sure it's nothing.

I'll let you know when we level off.

With the first alarm still beeping in the cockpit,

things become even more confusing.

Their master caution alarm goes off.

It could indicate that some systems onboard are overheating.

We now have a master caution.

I'll get you an engineer, 522. Just a minute.

I find him very hard to understand.

His accent is quite thick.

Flight 522, what can I do for you?

The ventilation cooling fan lights are off.

Sorry. Can you repeat?

While the pilots and ground engineers

try to troubleshoot the two alarms,

most passengers have no idea there's a problem until...

Everyone stay calm. Please remain seated.

Everyone please put the oxygen

masks on completely over your mouth and nose.

The protocol was immediately to secure yourself,

grab an oxygen mask, stay in your seat.

If you can help passengers without getting up,

you could help them and you should help them.

But you would not risk the safety of any cabin crew member

to go and help a passenger which is five or six rows further up.

Their procedure would be to grab their mask,

don it, and wait for the aircraft to level off or

commence with a descent.

No one in the cabin knows what the problem is.

They're waiting for information from the cockpit.

The pilots are unaware that the oxygen masks

in the cabin have dropped.

And they still don't know why their takeoff configuration

warning is on or why their systems are overhearing.

Both of my equipment cooling lights are off.

This is normal. Can you please confirm your problem?

But the engineer on the ground is struggling

to get a clear picture of what's happening in the air.

They are not switched off!

Can you confirm

that the pressurization panel is set to auto?

Where are my equipment cooling circuit breakers?

Behind the captain's seat. Can you see them?

What's going on?

There's something wrong with the electrics on 522.

I had something to pick up

from operations so I was, I was there.

I figured, oh not again. One of our problems. So I left.

Well good luck.

The problem doesn't seem serious,

but as the plane continues to climb, passengers still

haven't received any information from the cockpit.

Helios 522, can you see the circuit breakers?

And now the engineer on the ground

loses contact with the aircraft.

Helios 522, can you hear me?

It's less than 30 minutes after take-off.

And flight 522 is still on course.

The plane is high above the Mediterranean Sea -

and headed straight towards Athens.

August the 14th, 2005.

A Helios Airways 737 with 1-hundred and twenty-one people

onboard is circling in the sky near Athens.

Helios 522, can you hear me?

Shortly after leaving the island of Cyprus,

two different alarms had been triggered on the plane.

The flight crew was trying to solve

the problem with the help of ground engineers.

But now radio contact with the plane has been lost.

Air traffic control can't get any response

from the captain or co-pilot.

The flight to Greece normally takes an hour and a half

but the passenger jet has been in the air for over two hours,

circling in a holding pattern.

We heard that there was an airplane which was

flying into Greek territory and had no communication.

Everybody's mind was going to hijack or to terrorist.

More than 3-million people live in Athens.

A plane slamming into the city

could cause an incredible loss of life.

This is a runaway aircraft.

It's a possible hijacking or it's a possible terrorist act

so let's involve the military.

The Greek air force scrambles two of its most

sophisticated fighter jets to investigate the Helios plane.

Helios 522, do you read? Over.

But the pilots aren't getting any response.

One of the jets flies closer to the cockpit.

Someone is in the co-pilot's seat, slumped over the controls.

But there's no sign of the captain at all.

The fighter pilot radios air traffic control in Athens.

Athinai ACC,

there's one figure in the cockpit of Helios 522.

He appears non-responsive. Athinai ACC, checking the cabin.

He can see passengers in their seats,

but none of them react to the presence of the jet.

Then, the pilot sees someone moving in the cockpit.

Athinai Control.

There is one person moving in the cockpit of Helios 522.

Repeat there is one person inside the cockpit.

Helios, 522 do you read? Over. Helios 522. Over.

Flight HCY 522, this is Athinai radar control.

The F-16s continue shadowing the jet,

but there's no response at all from the cockpit.

One of them was actually

in a shooting position behind the 737.

The other one was nearby the cockpit and he was

trying to communicate visually with the person in the cockpit.

Suddenly, the 737 turns left

and begins to quickly descend.

Athinai ACC. Helios 522 turning sharply.

Following down.

From more than 10-thousand meters,

the plane drops towards the ground.

There is no structural failure. There is no fire.

There is no problem, obvious problem,

from the external view with the plane.

Helios 522. Over. Do you read?

Helios 522, do you read? Over.

Then 21-hundred meters above the ground,

the person in the captain's seat

acknowledges the fighter jet for the very first time.

But no words are exchanged.

Neither the fighter pilot nor local air traffic control

can make radio contact with the jet.

Just after twelve o'clock, almost three hours

after it took off from the island of Cyprus,

Helios flight 522 slams into the ground.

Athinai ACC. Helios 522 is down.

Repeat Helios 522 is down on Grammatiko Hill. Over.

Fire and rescue workers rush to the crash site.

There are no survivors.

Flight attendant Lazaros Temetzian is stunned by what

he hears at the company's operations center.

It was the most chaotic scene I've ever seen.

When I went back, our operations controller said that he

lost the aircraft and his eyes, he started to cry.

Helios is a small company, with just three jets.

Members of the cabin crew have been working together for years.

For Paul Symeonides,

news of the crash is particularly terrifying.

He's a flight attendant for the airline, and so is his fiancée.

I think that must have been the worst thirty minutes

of my life following that first image

because Victoria was flying that morning to Glasgow.

I had everyone and his brother,

every person we knew was calling me up to find out if I'm alive,

if Victoria's alive, what happened, why it happened.

At first we said it takes one hour and a half

to go to Greece, so probably it's not that plane

and it took about two or three hours later to know that

Paros and Maria was on the plane that crashed.

Andreas Prodromou's father didn't know his son

had been called to fill in on Flight 522.

I was told that a Helios aircraft was

lost by radar and air controllers couldn't contact it.

I got worried. I called Andreas' phone.

He always had it on and unfortunately

he wouldn't answer.

After that phone call,

I felt as if the ground was pulled out from under my feet.

It's the worst air crash in the history of Greece.

Most of the 1-hundred and twenty-one victims

are from Cyprus.

The small island nation declares three

days of mourning following the crash.

It's an eerie disaster.

For over an hour, air traffic controllers watched

the passenger jet fly in radio silence closer and closer

to Athens with no idea what was happening inside the jet.

Now, piece by piece,

investigators are trying to find out.

So we climbed over the hill and there we were,

you know, facing this situation

which was beyond any, any description.

I saw a great area in front of me which was burning,

it was black, burning, people spread, pieces of the airplane.

It is a truly nightmarish sight.

I hope that I never experience it again.

It was terrible, just terrible.

Investigators immediately start

looking for the cause of the crash.

In the early days, their efforts take a frustrating turn.

They recover the box containing the cockpit voice recorder,

but the recorder itself has been thrown clear.

It was difficult for us because we first,

first found the case of the CVR very badly damaged

and we could not find the, you know, the machine itself.

Investigators need to know what

happened to the pilots.

Without the cockpit voice recorder,

they have little to go on.

So keep looking. Let's hope we can find it.

Bodies recovered from the wreckage are brought

to the offices of Athens' chief coroner.

Autopsies add more mystery to the case.

Everyone on board the plane was alive at the time of the crash.

There were scenarios at the time

that they had all died in midair.

But the truth, they did not die from inhaling a toxic

substance in the airplane or from an explosion.

These people died on impact.

But if the passengers were alive the entire flight,

why didn't the pilot of the fighter jet

see any activity inside the cabin,

and who was at the controls as the jet circled over Athens?

When investigators find tissue samples in the remains

of the cockpit, they make a stunning discovery.

The person at the controls of the plane when it crashed

was flight attendant Andreas Prodromou,

a last minute addition to the cabin crew.

But why was he in the cockpit?

Was he trying to save the plane,

or did he deliberately fly it into the ground?

Several days after finding the outer case of the cockpit

voice recorder, investigators find the recording itself.

When chief investigator Tsolakis listens to the final

moments of the flight, it answers a vital question.

Mayday, Mayday, Mayday.

This was no terrorist act.

Helios Airways flight 522.

Prodromou was calling for help.

Mayday, Mayday.

Tsolakis hears five separate maydays on the tape,

even though none of them were heard

by air traffic controllers.

From the first moment that they saw someone

in the cockpit believe me, I was certain it was Andreas.

He wasn't a coward.

He knew something about planes,

and he had the capacity to do something.

In fact, Prodromou had his commercial pilot's license.

It was the first step towards his goal

of becoming a captain for Helios.

It's the sort of day I'd like to be out flying.

Oh you will Andreas.

But all of his training

wouldn't have helped save the jet.

When he was seen at the controls,

flight 522 had been in the air for almost three hours.

And the reason the Helios plane seemed to veer away from the

F-16s following it was because its left engine was out of fuel.

No matter what caused the alarms to sound,

the ultimate reason for the crash was simple.

The DFDR and the CVR gave us absolute proof that the

plane ran out of fuel and this was the cause of the crash.

Scheduled as a ninety-minute flight, the plane

didn't have enough fuel to stay in the air for over three hours.

But why had the plane flown so much longer

than it was supposed to?

Tsolakis now knows who was in the cockpit of the plane

and why it crashed.

But to fully understand the mystery,

he needs more information.

His investigators uncover a suspicious

history of maintenance issues with the Helios jet,

issues that could help explain what happened on flight 522.

Less than a year before the crash,

the same aircraft had suffered a rapid decompression.

Lazaros Temetzian worked on that flight.

I was in the back of the aircraft at the time.

There was a loud metallic bang, a clanging sound

and the oxygen masks dropped in the cabin.

Every step I was taking was difficult.

It was hard to move, uh hard to breathe.

In fact, I was, I was starting to pant, I was panting for air.

As the plane began an immediate descent

to 33-hundred meters,

all Temetzian could do was remain strapped in and wait.

Once the plane reached a safe altitude,

Temetzian inspected the rear door

and was shocked by what he found.

I noticed that the aft service door

was not fully locked.

The hinges on the top and the bottom of the door

were kind of displaced.

I could pass my hand right through.

There were no injuries and the plane made

an emergency landing, and the door was inspected.

But this wasn't the only problem crews had with this plane.

We would record faults in the cabin logbook

constantly and nothing would be done to rectify even these

small little problems in the cabin.

Engineers would take months to rectify

even the slightest problem in the cabin.

There were more recent problems as well.

A Helios ground engineer tells Tsolakis that on the very day of

flight 522, the 737 had another problem with its back door.

When we checked the flight log for the trip,

we saw that we'd have to do some unscheduled maintenance.

The plane had arrived in Cyprus just after

midnight on August the 14th.

The cabin crew had heard loud banging noises

and saw ice on the rear service door during the flight.

It was scheduled to take off again just hours later.

Soon after it landed, engineers began checking the problem.

To make sure there's nothing wrong with the seal

on the door, the engineers run a pressurization test.

During normal flight,

a plane's engines force air into the cabin.

To ensure oxygen circulates during the trip,

small valves in the rear allow some of it to leak out.

A pressurized airplane essentially is

sort of like a pressurized can.

We pressurize the airplane so that the people inside can

survive the environment that the airplane likes to operate in.

Switching digital pressure control

unit from auto to manual.

Without the jet's engines running,

the engineer uses the plane's auxiliary power

unit to force air into the aircraft,

and the cabin is pressurized for several minutes.

It's like looking for a leak in a tire.

In this case, what you're having to do is pressurize

the aircraft, use a bar, a barometer essentially

to monitor the pressure inside uh and look for leaks that way.

But there's no indication any air

is escaping through the back door.

In this case, they felt that it was all right

and they completed the test.

The entire jet seems to be in good working order.

After performing a series of additional routine maintenance

procedures, the engineers signed off on their technical log.

Investigators are faced with a dead end.

An explosive decompression

could have explained the tragic events of flight 522.

If the oxygen had been suddenly sucked out of the jet,

everyone onboard could have been overcome.

But not only did engineers check the problem, when the F-16s

approached the plane near Athens, no damage was seen.

There was no indication that the fuselage was punctured.

Investigators are still struggling to solve the mystery.

What had overcome the passengers and crew of Helios flight

522, and why was one flight attendant apparently unaffected?

The discovery of one small switch holds

the key to the entire crash.

The crash of Helios flight 522

is one of the most mysterious air disasters ever.

Helios 522, do you read? Over.

All investigators know for sure is that shortly

after takeoff the crew stopped communicating

with air traffic controllers.

Helios 522. Over. Mayday.

Then, after two and a half hours in the air,

one of the plane's flight attendants

was seen at the controls.

Eventually the plane ran out of fuel and crashed,

killing 1-hundred and twenty-one people.

But investigators are stumped.

They still don't know what had happened to the plane's

captain or the rest of the crew.

Tell me about what happened the day of the flight.

They concentrate on the conversation

between the pilot and the Helios engineer shortly after takeoff.

As the plane passed through 37-hundred meters,

an alarm sounded in the cockpit.

Operations, this is flight 522. Over.

Flight 522, what can I do for you?

We have a takeoff config warning on.

Pardon?

Our takeoff config warning is on.

Usually, the takeoff config warning

is only triggered on the runway,

but wreckage recovered at the crash site

reveals no problems with the plane's flaps,

landing gear or anything else that could trigger the alarm.

So why had it sounded?

Chief investigator Akrivos Tsolakis focuses on a small

control panel found in the wreckage of the ravaged jet.

Are you sure this is the way it was found?

It hasn't been moved at all?

We were lucky.

Finding this panel which had the switch

on the manual position was a major one.

The P-5 pressurization panel ensures that

passengers have enough air to breathe, even at high altitudes.

Normally, pressurization takes place automatically.

As the jet climbs, its engines force

air into the plane as they power it through the sky.

But when the pressurization switch is set to manual,

both the captain and co-pilot are responsible

for maintaining the cabin atmosphere using a controller.

So explain again how you tested the pressure.

I went into the cockpit.

I turned the pressurization switch to manual.

Tsolakis learns that during the early morning

maintenance check on Helios 522,

ground engineers had turned the P-5 switch to manual.

That allowed them to use the onboard generators

to test the pressure seals on the plane's rear door

without starting the engines.

When the test was over,

they didn't turn the switch back to automatic.

The procedure of pressurizing the aircraft

has to do with setting the pressurization

system from auto to manual.

They were supposed to return

the uh selector to the auto position.

Several hours later, when the flight crew entered

the cockpit, the pressurization switch was still set to manual.

It's bright today. Are you almost through?

Pardon?

But neither the pilot nor co-pilot saw it.

As a result, after takeoff the cabin would not pressurize

automatically, and the higher flight 522 climbed

the thinner the atmosphere became.

Not turning the switch back to automatic

was a deadly hidden danger.

Are you sure this is the way it was found?

It hasn't been moved at all?

Tsolakis believes this panel could be

the key to the disaster.

Leaving one switch on manual could have led to all

the other problems the plane faced.

To prove he's right, he takes an unusual step.

Four months after the disaster, he takes an Olympic Airlines

737 on the same route flown by the Helios jet.

If he's right about what caused the crash,

this plane should react exactly like the doomed airliner did.

Are we ready to go?

When there is a complicated accident like this,

I think reenact, reenactments should, should be performed.

Of course it's expensive to have a jetliner flying

for three or four hours but it is worth it if you have to come

with some results which benefit to the overall investigation.

Make sure the P-5 is set to manual. It's hard to see.

In the cockpit,

Tsolakis has the crew turn the pressurization switch to manual.

A green light indicates it's no longer on automatic

but in the bright glare of an early morning departure

the light is hard to see.

As the reenactment flight climbs,

oxygen is thinning quickly in the aircraft.

The same thing happened on the Helios flight,

triggering an alarm.

What is it?

The takeoff config warning?

The alarm sounded and that alarm was misinterpreted.

Most of the flight crew they will never face

an alarm with non-pressurization in all of their flight career

because it's a rare event.

Tsolakis confirms that the alarm went off

because of the dangerously low air pressure in the aircraft.

But he also discovers that the sound itself is

identical to the takeoff config warning.

We have a takeoff config warning on.

But even if the flight crew did misinterpret

the first alarm, they still had another chance to determine

what the real problem was.

At almost 5-thousand meters, the plane's master caution

light flashed on and stayed on for almost a minute.

We now have a master caution.

But once again the pilots misinterpreted

the cause of the alarm.

The master caution light can indicate that the plane's

systems are overheating.

But it can also tell pilots the oxygen masks are down.

In this case, it was doing both at the same time.

But since the crew didn't think

they were having pressurization problems,

they focused on the plane's cooling systems.

The alarm about the non-cooling

was a side effect of non-pressurization.

Actually it was not really that there was a high temperature

inside the avionics bay, but it was the sensors

that were supposed to measure the temperature

and the pressure in that area sensed that something was wrong.

On the recreation flight,

investigators monitor instruments recording

the same events occurring onboard their aircraft.

At the same time,

they also begin to feel the effects of the lack of oxygen.

The first feelings you'd start to have

were your ears would pop

and you'd start feeling pressure in your sinuses.

Uh as you climb higher, you begin to feel almost giddy.

It's almost like having a couple of drinks of alcohol.

The dwindling oxygen levels could also help

explain some of the crews' bizarre behavior.

Such as, when the ground engineer

asked about pressurization...

Can you confirm that

the pressurization panel is set to auto?

Captain Merten ignores the question

and responds with one of his own.

Where are my equipment cooling circuit breakers?

You really don't notice it at first.

It's amazing how subtle it can be in the early phases.

They'd start feeling dizzy.

They'd begin to lose the ability to think coherently.

In a way it traps you in the situation.

You can't react to anything.

Eventually, you're gonna lose consciousness.

Tsolakis believes that the captain may have been

checking on the circuit breakers behind his seat

when he and the co-pilot finally ran out of air.

And, unlike in the cabin, the oxygen masks in the cockpit

do not automatically deploy if the atmosphere begins to thin.

Helios 522, can you hear me?

On the other side of the locked cockpit door,

no one in the cabin would have known

that the plane was now flying itself.

Nor would they have realized that

a limitation of the passenger oxygen system had sealed

the fate of everyone in the cabin.

Passenger masks are supplied by a chemical

generator above their seats, but the generators only produce

enough oxygen to last about twelve minutes.

Well the problem with the passenger masks

is for one thing they're not designed to keep you

oxygenated at a high altitude.

What they're designed to do is give you enough oxygen

so that you can survive

until the pilots get the airplane down to a low altitude.

In almost every event where we've had a decompression,

that's been perfectly adequate.

For those who did put their masks on,

they would have remained conscious for several minutes

until their oxygen ran out.

Then they too would have passed out.

Once you get up to 34-thousand feet,

you're talking useful consciousness

of thirty to sixty seconds.

Most of the people, once the hypoxia begins to cause them

to lose consciousness, they're just gonna go to sleep.

Without a flight crew,

Helios 522 would have continued to Athens on autopilot.

When the crew didn't take control,

the autopilot would have put the jet in a holding

pattern as it flew over the airport.

Exactly the same thing will happen on the reconstruction

flight if cabin pressure isn't restored.

Tsolakis asks the co-pilot to reset

the P-5 panel to auto before the jet continues to climb

to its cruising altitude of just over 10-thousand metres.

Then, as it approaches Athens, Tsolakis also has

an F-16 shadow the jet performing the recreation.

He wants to confirm that it was Andreas Prodromou

at the controls of flight 522 when it went down.

We dressed one of our guys

with the uniform of the steward.

He came in, he sat on the captain's chair,

and the F-16 was looking at him.

He was confirming that it was exactly what

he saw on the accident plane.

The reconstruction also answers another

question about the tragic fate of Helios Flight 522.

The cockpit voice recorder

picked up several strange noises.

They're heard just before Prodromou enters the cockpit.

Tsolakis confirms that these sounds were made by Prodromou

using the electronic keypad to unlock the cockpit door.

We confirmed all those items and during the

reenactment flight and it was very, very useful.

It filled a lot of gaps we had.

Okay, take it down.

For chief investigator Tsolakis,

the reenactment flight has been convincing.

There was no dramatic cabin failure.

Instead, a series of small mistakes and misunderstandings

had led to the worst air disaster in Greek history.

Fifteen months after the crash,

Greek authorities release the official

report on Helios Airways Flight 522, but mysteries remain.

What was happening in the cabin

while the doomed airplane flew towards Athens.

And why was Andreas Prodromou the only one

conscious at the very end.

The crash of Helios Flight 522 was the worst

disaster in the history of Greek aviation.

Like many crashes, it was a fatal combination

of mechanical problems, and human error.

The final accident report details a tragic series of

oversights and false assumptions made by the flight crew.

Problems that could have been easily prevented turned

deadly for all 1-hundred and twenty-one people onboard.

Where are my equipment cooling circuit breakers?

Behind the captain's seat. Can you see them?

But what the final report does not do is

explain what happened in the cabin of the plane.

What actions did the flight attendants take?

And why was Andreas Prodromou still conscious

after almost three hours?

Interviews with Helios safety instructors and crew members

paint a tragic picture of what may have occurred.

Everyone, please your masks on.

We're not sure what the trouble is but remain calm

and please remain seated.

Prodromou was sitting at the back of the cabin.

When the oxygen masks fell,

he would have waited for instructions from the cockpit.

The flight attendants sitting at the front of the plane would

have done the same, but none of them would have waited forever.

We made it an issue at Helios

to uh to emphasize that cabin crew

should not entirely depend on their procedures,

but to think on their feet

and to adapt to any impending situation.

In most depressurizations,

the plane descends quickly.

But as minutes passed on the Helios flight,

the plane continued to climb.

Unsure of what was going on,

Prodromou would have tried to contact the flight crew.

Captain? Captain Merten?

But he gets no response.

Can you give us an update please

With no word from the cockpit, he would have soon

realized that this was not a typical depressurization.

When there was no call out from the cockpit

and the aircraft didn't start an emergency descent,

there was absolutely no protocol.

It would be, they would be winging it.

By now, Prodromou must have felt

that something was terribly wrong.

But to find out what the problem was he had to leave his seat.

The oxygen available on a 737 is of course

the drop-down oxygen.

Ten percent of those masks are available

for the crew in case of a de-pressurization incident.

There are extra masks per every seat row.

Taking advantage of the extra passenger masks,

he could have made his way to the front of the plane,

a process cabin crew called monkey swinging.

But if more than twelve minutes had passed, his girlfriend

and the other flight attendant may have still been

in their seats and, like the passengers, overcome by hypoxia.

But Prodromou was a scuba diver

and a former soldier in the Cypriot special forces.

His training may have helped him to stay alert a little longer.

Andreas was not a coward.

He was a brave person, fearless, brave and very calm.

But to survive after the passenger oxygen system

stopped working, he needed another solution.

The 737 had four portable oxygen bottles.

Each one could last more than an hour.

All four bottles were found at the crash site.

Three of them appeared to have been used.

While the F-16 pilot saw Prodromou in the cockpit

just before the crash,

it may not have been the first time he had gone in.

As he did at the end of the flight,

he could have used the security code to unlock the door earlier.

The procedure would be to enter the flight deck

via the cockpit door,

initially to bang on the door and then if no response is

forthcoming to enter the code and enter the flight deck.

During the accident investigation,

DNA was discovered on an oxygen mask in the cockpit

that matched the co-pilot's.

It's possible Prodromou used it to try and revive him.

You can still revitalize somebody

for quite an extended period of time if you

get to them before major brain damage has set in, and that's

somewhat a variable situation depending on the person,

depending on how long they're exposed to high altitude.

But if he was in the cockpit earlier,

why did he leave?

No one will ever know.

He probably was a little bit disoriented,

a little bit confused.

He's reacting a lot slower than he normally would.

What was his state of mind?

What was his physical condition?

We think that he knew what was really the problem

but is that the real situation?

It's a real question.

After three hours in the air,

everyone who didn't have bottled oxygen

would have been unconscious.

As it approached Athens, flight 522 was now a ghost plane.

Most of the victims,

uh they probably still had heartbeats when the airplane

crashed but almost certainly were in an irreversible coma.

Hypoxia is no more painful than falling asleep,

but for Andreas Prodromou

the flight must have been a nightmare.

As the F-16s roared to meet the jet,

and with his oxygen running out,

he must have known that he too was almost out of time.

Yet, to the very end he didn't give up.

Prodromou made one last attempt to save the plane.

When he returns to the cockpit, the young flight attendant

who dreamed of becoming a pilot calls for help.

But no one can hear him,

probably because the radio was still tuned to Larnaka,

the airport on Cyprus where the flight had taken off.

Fighting hypoxia and struggling to control an airplane

larger than any he had ever flown,

Prodromou was in an impossible situation.

Even if he could have landed the plane, it was now too late.

Flight 522 was out of time and fuel.

There are pictures of Andreas in Cyprus, in the cemetery

where he and his girlfriend Charis are buried side by side.

As his father, my son is in front of me.

Wherever I go he is always there. He left a very big gap.

We will never get over it.

There are pictures in Greece too.

On the hill north of Athens where Helios flight 522 crashed,

there are faded photographs of many of those who died.

Bleached by the brilliant Mediterranean sun,

they gaze over the rugged, ancient terrain,

silent witnesses to one of the world's most bizarre

and tragic airline disasters.