Chilling words of fighter jet pilot who witnessed 'ghost plane' crash that killed all 115 passengers and crew onboard

The chilling words of a fighter pilot who witnessed a plane crash into the mountainside have resurfaced online.

In August, 2005, Greece was devastated when Helios Airways Flight 522 crashed into a mountainside just north of Athens - killing 115 passengers and six crew members onboard.

The plane had departed from Larnaca in Cyprus just after 9am on 14 August and was destined for Prague, via a quick stopover in Athens.

However ground crew in the Greek capital would be left baffled after their radio calls to Flight 522 went unanswered. The aircraft was last heard from shortly after departing Larnaca airport when the pilots reported an air conditioning warning to ground staff.

Fighter jets were then scrambled after air traffic control staff after they were unable to get in contact with the pilots amid concerns of a hijacking or terrorism incident.

But what they'd find was arguably even more chilling.

The aircraft crashed near the village of Grammatiko (LOUISA GOULIAMAKI/AFP via Getty Images)

After locating Flight 522 circling aimlessly above Athens, fighter pilots noted the first officer slumped in his seat at the controls, while the captain's seat was left vacant. Inside the cabin, passengers were unconscious, despite oxygen masks dangling in-front of them.

The fighter jet pilots were helpless to watch on as the 'ghost flight' flew aimlessly around in the sky, well aware of the impending disaster which awaited.

All passengers and crew onboard the flight were alive, but unconscious, with the exception of flight attendant Andreas Prodromou who was awake and desperately attempting to steer the plane to safety. While a qualified pilot, Prodromou had no experience with flying the Boeing 737-31S plane and was unable to prevent the flight's final destination.

Just under three hours after take off Flight 522's engines failed within 10 minutes of each other and Prodromou pointed weakly down to the fighter pilots, who were helpless to watch as the aircraft slammed into a hillside near the village of Grammatiko.

The incident was caused by a loss in cabin pressure (Milos Bicanski/Getty Images)

The devastated words of one of the fighter jets who witnessed the crash would later resurface online.

In the audio, which is between the pilot and crew on the ground, the pilot can be heard saying: "Mayday, mayday. Mambo, we have a civilian plane crash. We have a civilian plane crash. Mayday, mayday.

"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.