Why do we get so emotional on planes? Photo: Kevin Winter/Getty Images

Crying more on planes is a well described phenomena for any flyer. So much so, that Virgin Atlantic has introduced special trigger warnings before weepy movies to let passengers know that they’re about to see a tear-jerker.

It’s the second time the airline has added the emotion notices — they first trialled them in 2011 to coincide with a particularly heart-wrenching collection of films showing on their in-flight entertainment system.

“It’s well-known that emotions are heightened on a flight, and we often spot customers shedding a tear over a movie,” Carly Swaine, a member of the Virgin Atlantic cabin crew said.

“There are a few real tear-jerkers on board at the moment so the notifications help reassure customers that it’s fine to let their feelings show, or to call the crew for a cup of tea.”

When the airline first introduced the emotional health warnings in 2011, it said that a social media poll they ran found that 55 per cent of flyers said they had experienced heightened emotions while flying.

But why do get so emotional in the air? There has been no specific scientific research that delves into the phenomenon, but there are many theories.

In a study about adult crying behaviour published in 1997, a team of researchers at Tilburg University in the Netherlands found that most adult crying episodes took place at home or another intimate place, like an office or car, rather than outside in the public.

And another research paper by a professor at the University of Minnesota, which studied the phenomenon of grieving while driving, found that some bereaved people seem to save their grieving for times when they drive, because that is when they have the time and privacy to think and feel.

What both these studies could teach us about crying on aeroplanes is that we might be more prone to getting emotional in the air because we are isolated — we are sitting in a metal tube 35,000 feet in the air with none of our usual daily distractions, no mobile phones, and the inability to get off. Flying, like driving or being home alone, forces us to think and feel. So when we chuck on a romantic movie, these bottled up emotions can get the best of us.

What the Tilburg University’s research paper also found is that separation is the most likely situation that elicits crying in adults. And getting on a plane often means you are being separated from your family and friends back home, even if it is for an exciting holiday.

But other theories suggest it could be something more physical. Medically, the lower air pressure of an aircraft can cause changes in your mood, personality, behaviour and cognitive functioning.

“The oxygen levels on a plane are equivalent to about 8,000 or 10,000 feet, and we do know that judgment is impaired as oxygen levels lower,” Professor Drew Dawson, Director of the Appleton Institute at Central Queensland University told The Huffington Post Australia.

“And I suspect people whose respiratory function is not quite perfect will probably have a little reduction in saturated oxygen levels in their blood stream and that could account for it. It’s only a hypothesis, I have no evidence to this. But it might explain it.”

Or maybe it is something more obvious, like the fact flying is cramped and tiring, and you never really get a good night’s rest.

But whatever the reason may be, if you’re worried about sobbing embarrassingly on a flight, steer clear of The Notebook. You won’t be able to help yourself.