The never-ending nightmare that is commercial flying just added a rather horrifying new potential mishap to its roster. On Thursday morning, passengers on a Jet Airways flight traveling from Mumbai to Jaipur, India, began experiencing headaches and nosebleeds. The flight eventually deployed oxygen masks and made an emergency landing. The cause? A crew member forgot to flip the switch to pressurize the cabin. Of the 166 passengers on board, 30 experienced symptoms, and five were sent to the hospital to get their ears, noses, and throats evaluated.
According to a statement by Jet Airways, the flight crew has been “taken off scheduled duties pending investigation.”
A Ryanair flight from Croatia to Dublin encountered the same situation in July and had to make an emergency landing after deploying oxygen masks (one flyer even tweeted out a photo of his bloodied mask). And, of course, there was the tragic incident this April of the woman who died after being partially sucked out of a Southwest Airlines plane window that was broken by an engine explosion.
Stories like these perpetuate the fear we all have when stepping into a steel behemoth whizzing through the sky at 36,000 feet: that something completely out of our control will go wrong, causing our brains to ooze out of our ears. While that won’t actually happen, here’s what does happen in the event of loss of pressure in an airplane cabin.
How airplanes are pressurized
All airplane cabins are pressurized to simulate the amount of pressure felt at 8,000 feet. Pressurization happens via the engines, which compress incoming air, heat it up, and then divert some of that hot compressed air to the cabin. On its way to the cabin, the air temperature is lowered via two different cooling systems and then an expansion turbine, which “cools it the way blowing with your lips pursed results in a cool flow of air,” according to Air & Space Smithsonian. Finally, the cooled air is combined with air already in the cabin using a mixer, or manifold.
Pressure in the cabin is maintained by the opening and closing of an outflow valve, which releases incoming air at a rate regulated by pressure sensors (Air & Space Smithsonian says to “think of a pressurized cabin as a balloon that has a leak but is being inflated continuously”). This is not only for passengers’ comfort but also for operational purposes. If planes were pressurized at ground level, they would have to be made with heavier materials and use more fuel.
So what happens to your body when an airplane cabin is not pressurized?
Just like the human body can only survive in a certain range of temperatures, it can only survive in a certain range of pressures. Boyle’s law states that the volume and pressure of gas are inversely related, meaning when air pressure drops like it does in an ascending airplane, gas — like what’s held in our noses, ears, lungs, and intestines — expands.
When a plane is ascending and descending, atmospheric pressure changes, and our bodies try to equalize the internal pressure to match the outside environment.
The equalizing process is usually assisted by an air crew ensuring that the cabin is pressurized, but even with that help, many people still feel effects of altitude change through things like ears popping, which happens because your middle ear is trying to equalize pressure with the surrounding atmosphere.
If a cabin crew does not remember to pressurize the cabin, as with the Jet Airways flight, the gases in your body will expand beyond what they are supposed to, rupturing tissues and causing bleeding. These injuries are called barotrauma.
In scuba divers, barotrauma is commonly referred to as “the bends”: Nitrogen can dissolve into the blood when a body is under pressure, but when a diver shoots upward, the gas quickly expands into bubbles and causes barotrauma, according to a New York Times interview with Dr. Matthew Fink, neurologist in chief at New York–Presbyterian Hospital/Weill Cornell Medical Center.
According to Dr. Divya Balasubramanian, a doctor of osteopathic medicine in Dallas, ears, sinuses, and mouth cavities most commonly hold manifestations of barotrauma. Bleeding starts with the ears and nose because those are the smallest places in your body that trap gas; blood can also come out of your oral cavities. If the conditions persist, the effects could eventually spread, possibly causing cardiovascular or lung issues.
“Your lungs and intestines will be able to handle it better, but it would eventually affect those parts of the body the more volume expansion that occurs in the area,” Balasubramanian says.
Of course, the chances of you experiencing a life-threatening shift in barometric pressure while flying are rare. In fact, 2017 was dubbed the safest year of air travel with no commercial passenger deaths — a significant improvement from 2005 when there were over 1,000 deaths on commercial air carriers. But statistics are of little comfort when you’re strapped into an airplane seat 36,000 feet up.