Settling into his window seat on flight FR1879 from Thessaloniki, Greece, to Memmingen, Germany, on the morning of Friday, July 10, Serbian passenger Ljubisa Karovic, 61, would never have predicted that his choice of where to sit would become a life-defining, life-threatening moment.

The flight had been travelling for only ten minutes when passengers heard an enormous bang. The window next to Karovic’s seat on the Ryanair Boeing 737-800 had shattered. Despite being strapped into his seat, Karovic’s head and shoulders were sucked out of the window, and his entire torso was exposed to the elements for ‘up to two minutes’ according to his wife, Svetlana Grkovic, who clutched his legs to stop him falling out any further.

Karovic fainted three times throughout the ordeal. He was eventually pulled back into the plane by his wife and other nearby passengers and, 30 minutes later, the plane made an emergency landing back in Thessaloniki.

Nearly a week later, he is still in hospital recovering from his injuries which reportedly include severe friction burns and a hand injury. ‘His entire face was deformed and blood was pouring from his nose and mouth,’ his wife said. ‘His hand is particularly badly injured, and he’s got burns. He’s not able to communicate.’

But by some miracle, he is still alive.

To find out what can happen to the human body when it is wrenched halfway out of a plane at 20,000ft, we spoke to Dr David Carey, 63, a commercial pilot and ex-military specialist in aviation medicine with more than 40 years’ experience.

The biggest threat to someone’s life during an explosive decompression like this is the risk of what’s called hypoxia. This is a dangerous medical condition caused by being unable to transport the oxygen in the air to the body because of the change in cabin pressure. The important organs in your body such as the heart and the brain, need oxygen to function properly. Without it they will die.

At 20,000ft, the air is at significantly lower pressure than at sea level. The amount of oxygen in the air is fairly constant (around 20 per cent) but at lower pressure you cannot move it around to your organs. The reason why oxygen masks drop down from the ceiling when the cabin pressure drops is because those masks provide a higher oxygen content to compensate for the pressure loss.

Because Karovic’s head and right shoulder were out of the window the oxygen mask would have been inaccessible to him and quite probably his wife as she held his legs. The signs are obvious if someone is becoming hypoxic – they start becoming breathless then confused and incoherent and incredibly fatigued or weak until eventually they lose consciousness.

People with cardiovascular or respiratory issues are particularly at risk in this situation. Any underlying conditions such as chronic obstructive pulmonary disease, recent heart attacks, even asthma can put you at increased risk of a stroke, heart attack or death as a result of hypoxia.

Perhaps the most dramatic moment of this incident, and the moment that would have affected everyone on the flight, was the explosive pressure drop in the cabin. Flight cabins on commercial jets are kept at an equivalent atmospheric pressure to 8,000ft. Imagine going from that to 20,000ft in an instant. As the air moved from the (highly pressurised) cabin to the (low pressure) air outside, Karovic was pushed along with it.

Thankfully in a cabin the size of a Boeing 737, after the initial rush of air escaping through the shattered window into the atmosphere, the pressure would equalise. So apart from Karovic who was by the window, no one else would have been pushed towards it unless the damage to the plane was extremely significant. Any difficulty getting Karovic back into the cabin is likely to have been due to his repeated loss of consciousness, or even the concern of injury by dragging him back through the damaged window.

If the door had come off a small private jet, where the cabin pressure is kept at around 4,000ft, the initial decompression could have been far more damaging, pulling more people towards the hole in the plane, because the size of the opening was large compared with the cabin size.

The biggest medical issue the depressurisation could have caused – for both Karovic and the other passengers and crew – would be severe barotrauma to the inner ear and sinuses. It’s extremely painful, can feel like a terrible head cold in the sinuses and sometimes results in blown eardrums. It may leave you with blood coming out of your ears, nose and mouth – which can look extremely worrying – but does heal completely over time.

There are all sorts of minor things that can happen to you if you are faced with the wind speeding past you when a plane is moving at 590mph. It could lead to friction burn, muscle strains in the neck and shoulders, head and face lacerations. But while none of these would kill you, hypoxia will. If the brain is cut off from oxygen for a significant period of time, you will not survive.

The temperature is unlikely to have been a massive factor here. It is summer and the plane was over Greece. As a rule, temperature drops 1.98 degrees per 1,000ft. So if it was winter and zero degrees then it might be problematic if someone was caught outside for a long period of time, but in this case temperature was the least of his worries.

Karovic was extraordinarily lucky on two accounts. Firstly, the window shattered at just 20,000ft when the plane was still ascending. If this had happened at 38,000ft – the cruising altitude for a large commercial passenger plane – then not just he, but the entire crew and pilots and passengers would have fallen unconscious within 15 to 30 seconds if no oxygen had been supplied. The partial pressure would actually suck oxygen out of your lungs. But the risk of hypoxia is lower at 20,000ft.

Secondly, the incident took place during the day over Greece, a country where the land is mostly at sea level. Within moments of the explosion, the pilot abruptly descended to 9,000ft. This dive was exactly the right thing to have done and is likely to have saved Karovic’s life, given he didn’t have access to an oxygen mask with his head outside the plane.

By getting the plane low, the pilot increased the amount of oxygen available to Karovic and any other passenger who did not have their oxygen mask on.

Thankfully, events like this are extraordinarily rare – there were two similar events in 2018 – but much like motorways, commercial flights are one of the safest ways to travel. I’d say he has a very good chance of making a full recovery.

Dr David Carey is an aviation medicine specialist

As told to Rosie Beveridge