Last month, I was midway through an overseas flight and near the end of my in-flight movie when I discovered a vaguely salty liquid building up inside my eyes. Immediately diagnosing the rare secretion as tears, I thought back to the last time this non-gendered and totally acceptable phenomenon occurred in my life. It was on a plane just a few days prior.
While it's possible that the two on-board movies I watched, Steve Jobs and Inside Out, cause a disproportionate amount of proverbial dust to accumulate in all viewers' eyes, something seemed different. Sure enough, when I mentioned it to a few friends and colleagues, they revealed similar experiences watching movies and TV shows on airplanes: uncontrollable bawling during Miss Congeniality 2; soft, quiet sobbing during The Lobster; imbalanced laugh-cries during Infinitely Polar Bear. It turns out a portion of us have unknowingly been part of the Mile Cry Club all along.
A few years ago, Virgin Atlantic sought to explore this phenomenon as it tested new entertainment options for its flights. Curious if it should broadcast "weep warnings" before particularly sad in-flight movies, the airline commissioned a 3,000-person survey and a Facebook poll to understand if passengers do indeed cry when they fly. The results were telling: 55 percent of respondents reported intensified emotions during flights, and 41 percent of men admitted to hiding their tears from other passengers.
Of course, this combination of anecdotal evidence and corporate market research neither explains nor proves crying-while-flying. So is it actually a thing? Is there something about planes that triggers more movie-induced tears than normal?
The answer is up in the air (sorry, sorry).
In a review of scientific literature on crying among adults, psychologists Ad J. J. M. Vingerhoets and Lauren Bylsma found that "probably the most common emotional trigger [for crying] is a feeling of powerlessness or helplessness." Even amid a mix of other intense emotions, "powerlessness [is] in a central position that stimulates our tears."
Considering this finding, it's possible that the anxiety around surrendering control on airplanes renders us more vulnerable to crying. Lots of people are scared of flying, and it's not lost on the rest of us that to fly is to be trapped in a steel phallus traveling hundreds of miles an hour at 35,000 feet, left to the mercy of pilots we don't know and a vehicle that's always introduced to us along with emergency escape plans.
I travel overseas often, though, and don't have a flying phobia. Surely I've been conditioned to tolerate—if not embrace—this high-stakes loss of autonomy. Plus I've watched movies in cars, buses and trains dozens of times and don't ever recall my powerlessness manifesting in tears, especially during a dispassionate biopic of a Silicon Valley executive.
A colleague wondered if lower oxygen levels could be a factor. Maybe crying is a side effect of spending extended periods of time at high altitudes, when there's less oxygen in the air we breathe?
I looked into it, and there are some compelling connections. Airlines are required to keep the cabin pressurized to regulate oxygen levels–roughly equivalent to what we'd experience at 8,000 feet above sea level. Some psychologists have found links between altitude and emotion, observing adverse mood states when people have lower levels of oxygen in their bloodstream. An even stronger correlation exists between altitude and fatigue: With less oxygen making it to our cells than when we're on the ground, we become more tired, particularly during long periods of exposure like an overseas flight. And when we're tired, we have a lower threshold for tears.
"A lack of sleep inappropriately modulates the human emotional brain response to negative aversive stimuli," says one study published in Current Biology. In other words, when we're tired—whether from sleep deprivation, stress, altitude or something else—our brains are less prepared to manage negative emotions, thus increasing our chances of experiencing and expressing sadness during, say, a tense on-screen interaction between Michael Fassbender and Kate Winslet.
Planes are also bridges between travelers and sentimental moments or places. If you're flying somewhere, there's a good chance you enter the flight feeling nostalgic or excited. A friend recently described her anticipation on a long flight home, and how she felt more prone to tears because she was already experiencing all the feels of returning to loved ones.
Underlying this wide range of psychological and physiological circumstances is the simplest and perhaps most likely explanation for airplane weepiness: We tend to be fully immersed in in-flight entertainment, without the usual distractions of text messages, emails, social media feeds and news updates. As one academic paper suggests, there's something hyper-intimate about in-flight movies and TV shows, especially now that most airlines offer personal screens and headphones. This setting could create a perception of solitude in which we might feel freer to let the tears flow when a seemingly cold business mogul embraces his daughter before a new product launch.
Nonetheless, there is still no definitive proof that the Mile Cry Club has any more members than its sex-themed predecessor. Tonic recently polled more than 100 Twitter users and found that only 30 percent are more emotional when they fly—which could mean the sampling didn't account for factors like long flights and consumption of in-flight entertainment, or that I've falsely extrapolated my own emotional tendencies to a population that isn't nearly as moved by Aaron Sorkin screenplays as I am. Either way, it's a curious phenomenon; and as long as plane seats offer arms for us to rest on, perhaps they should also consider offering shoulders for us to cry on.