Shocking case of 'ghost plane' that killed all 121 onboard after all passengers and pilots passed out on flight

Back in 2005, all 121 people onboard a flight were killed after all passengers and pilots passed out on the ‘ghost plane’.

In this shocking case, Helios Airways Flight 522 ended up crashing into a hillside just north of Athens as a fighter jet watched on helplessly.

Just after 9am on 14 August, the flight had set off for its journey from Laranaca, Cyprus, to Prague with a brief scheduled stopover in Athens. But it was found that within hours the plane’s engines had failed.

It was last heard from shortly after take-off, as the pilots reported an air conditioning warning to ground staff. And ground crew in the Greek capital were dumbfounded as their radio calls to Flight 522 weren’t answered.

There were 115 passengers and six crew onboard (LOUISA GOULIAMAKI/AFP via Getty Images)

With air traffic control staff concerned there might be a hijacking of terrorism incident, fighter jets were called in as they located the aircraft aimlessly circling over Athens.

Chillingly, they then spotted the first officer slumped in his seat with the captain’s seat empty.

And as they continued to scour the plane, they could see all passengers sat unconscious while unused oxygen masks dangled in front of them.

Clear that disaster awaited them, the fighter jet pilots could see just one flight attendant awake; Andreas Prodromou.

Desperately attempting to steer Flight 522 to safety, the qualified pilot had no experience with flying the Boeing 737-31S plane and was unable to prevent the flight's final destination.

And just less than three hours after it had taken off, the aircrafts engine failed within 10 minutes of each other.

The lone conscious flight attendant pointed weakly down to the fighter pilots who could do nothing but watch as the passenger plane slammed into a hillside near the village of Grammatiko.

There were no survivors (LOUISA GOULIAMAKI/AFP via Getty Images)

Audio later surfaced online, revealing the devastating words of one of the fighter jet pilots.

"Mayday, mayday. Mambo, we have a civilian plane crash. We have a civilian plane crash. Mayday, mayday,” they said to ground crew

"Mayday, mayday. Athens, the civilian plane crashed to a mountain peak."

Listen to the clip below on YouTube:

An investigation into the crash would later reveal the tragic crash occurred due to loss of cabin pressure, causing all onboard to experience the effects of hypoxia.

It was later theorised that the aircraft's cabin pressurisation switch had been left in 'manual' rather than 'auto' - leading to the depressurisation as the flight climbed into the sky.

Families of the victims would later file a lawsuit against Boeing in 2007, which was later settled out of court. Meanwhile, six former Helios Airways employees were charged with manslaughter by a Greek court in 2008, but the case was ultimately dismissed in 2011.

Helios Airways would cease operations in 2006.