In 2011, Virgin Atlantic Airlines started putting “emotional content warnings” before some of their in-flight movies.

And not because they were graphic or violent movies, the movies were just sad. These tongue-in-cheek warnings were a response to a phenomenon that many fliers have anecdotally noticed.

Namely, that they’re more likely to cry while watching a movie in the air than on the ground. Despite the number of people who report being members of the Mile Cry Club, there’s actually not a ton of research on what causes us to be extra weepy on planes. But there are some hypotheses flying around. [♪ INTRO] No matter how chill a baby is on the ground, it’s not unusual to find them screaming and crying when the plane takes off.

A lot of the time, babies and young children crying on flights aren’t just tired or hungry. They’re uncomfortable. See, air pressure inside your ears is regulated by narrow passages called the eustachian tubes, which keep the pressure inside your ears the same as the pressure outside of them.

When you need to change the pressure inside your ears, the tubes open up and cause your ears to pop. But the muscles that control your eustachian tubes can’t always react as quickly as a plane changes altitude, which can mean the pressure inside your ears is different from the pressure outside. And that pressure difference can cause the eardrum to stretch, which can be painful.

The smaller your eustachian tubes, the more trouble you might have with airplane ear, so infants, with their tiny tubes, have the deck stacked against them. Many adults are able to offset this effect by chewing gum, yawning, or using earplugs, but young children don’t really have those options. So a lot of the time, they’re just hanging out in pain during a flight.

But despite being better able to regulate ear air pressure, adults can still be crybabies on planes. In fact, a 2011 survey by Virgin Atlantic found that 55% of respondents reported experiencing heightened emotions while flying. The reasons for that could be physiological or psychological.

It might be related to hypoxia, or low oxygen levels. Even though the airplane cabin is pressurized, it’s not pressurized to the equivalent of sea level. It’s more like being at an altitude of 1,500 to 2,400 meters high.

Which means that while we’re not going to like, lose consciousness, we’re breathing slightly less oxygen than we typically are on the ground. The lower oxygen levels at higher altitudes have been associated with increased fatigue, increased depression, and lower inhibition, plus other cognitive and mood effects. Our bodies can compensate for these changes over time, so if you’re hiking or living at higher altitudes, your body will adjust after about 24 hours.

But most plane flights aren’t that long, so our bodies and brains don’t have a chance to adjust to those lower oxygen levels. And if you’re feeling more depressed and irritable than usual, plus you can’t regulate your emotions or reactions as well, that’s a prime cocktail for getting a little weepy. Now, how much of this applies directly to plane flights is a little unclear, but it does suggest that there’s a connection between emotions, altitude, and oxygen.

And oxygen levels aren’t the only thing that might contribute to tear-inducing tiredness on airplanes. Airplanes keep their humidity levels at about 10-20% to prevent structural damage to the plane, which is way lower than the 35-65% humidity that we tend to find more comfortable. And dry air means we lose more water from our bodies through evaporation and breathing.

Turns out even mild dehydration is enough to make us feel fatigued. And whether sleepiness comes from low oxygen or dehydration, or just having had to get up really early that morning because the plane left at 6 o’clock for some reason, being tired makes us more emotionally reactive. The more emotionally reactive we are, the more prone we are to crying.

But it’s not just physiological changes that could lead to you sobbing in seat 23F. There may be psychological factors at play as well. Some media scholars have proposed that despite being jammed in a tube with 150 strangers, the act of watching movies on a plane is more intimate than our typical media consumption.

The screens are much closer than we usually sit to a TV, and we’re listening with headphones. Plus, when we’re in the air, we can’t be on our phones or making dinner or doing a million other things while watching. That physical closeness and intentness may draw us more into movies than we usually are.

And if we’re more engaged, they’re going to have more impact on us. Or, you know, it could be the fact that air travel is stressful. Up to 40% of people have some degree of fear of flying.

But even for those who don’t, timing your travel, getting through security, navigating through the hustle and bustle, keeping up with your luggage, a lack of control and dealing with delays can be frustrating or tense. And anyone who’s ever held it together through a super stressful day and then cried because the person at the drive-through forgot to put honey mustard in your bag, can attest to the fact that when we’re stressed, we have a tendency to cry at things we typically wouldn’t cry about. Like, say, the movie Miss Congeniality, which the first four times I saw it were fine.

Not that I’d know anything about this. Or maybe we’re primed to be emotional on flights because we’re already experiencing emotions related to our trip. Maybe you’re sad to be leaving vacation or happy to be heading toward home and people you love.

In the same way we might cry watching movies after a breakup because of the emotions we’re already experiencing, we may do the same during travel. Of course, all of this varies by individual. People who are elderly or have other health conditions are often susceptible to physiological changes, and people’s subjective experiences of travel are going to be different.

It’s hard to say for sure exactly what’s going on, because there just isn’t a lot of research on this specific phenomenon. But whatever the reason, no one will judge you if you keep tissues in your carry on. Just bring enough to share.

Thanks to our patrons on Patreon for supporting this video, and all the other great work that people here do. Your support, if I think about it on a plane, is probably going to make me cry. We couldn’t do what we do without you.

Patrons also get access to a bunch of perks, like our private Discord server, monthly patrons-only podcast, and peeks behind the scenes, including a blooper reel. To learn more about becoming a patron, head over to Patreon.com/scishow. And thanks for watching! [♪ OUTRO]