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I was recently getting ready for a long-haul flight when a friend noticed what I had in my carry-on luggage. Along with my daily essentials, I packed a puffer jacket, thick socks, and a winter hat. “Aren’t you heading to Vietnam?” He asked. “I’m pretty sure it’s hot in there.”
“These are not for Vietnam,” I told him. “They’re for the plane.”
Airplane cabins remain very cold. What’s more, these frigid temperatures are absolutely intentional, says Bobby Laurie, former flight attendant and co-host of the travel and lifestyle talk show The Jet Set. Popular science.
“Look at the flight attendants the next time you get on a plane,” says Laurie. “It may be July in Miami and the temperature outside is 95 degrees, but everyone is wearing jackets and sweaters. They don’t really care what’s happening on the other side of the plane. They’re prepared for what’s going to happen inside.”
popular science Did you turn to Laurie to tell us the scientific reasoning behind this excessive cold and to find out why flight crews don’t simply increase the temperature on airplanes? In the end, all that cold air is much more than personal preference.
The average temperature of an airplane and its reasons
“The sweet spot for airplane cabin temperature is between 70 and 75 degrees,” Laurie says. It is an interior temperature that in most cases is pleasant. But because airplane cabins are already kept at lower humidity (typically 10 to 20 percent at cruising altitude, drier than most deserts) to help prevent corrosion of structures, the air can feel much colder.
Most commercial airlines keep their cabins in this temperature range for one main reason: to prevent passengers from fainting. On an airplane, the danger of someone suffering from hypoxia, a condition in which a person does not receive enough oxygen, often causing them to pass out, is a real possibility.
In fact, passengers fainting on airplanes happen more often than you think, Laurie says. It is especially common in red-eye flights. “People tend to be a little disoriented when they wake up in the middle of a flight,” he says. “A lot of times, they just stand up and immediately fall to the ground.”
This is due to the simulated air pressure in the cabin, which typically remains at an altitude equivalent to 6,000 to 8,000 feet above sea level. It is a mountain-level lift that acts as a compromise between maintaining the structural integrity of the aircraft (sea level altitude at a cruising altitude of 35,000 feet would force the aircraft to be excessively heavy and fuel-efficient) and keeping passengers comfortable.
While most people on board don’t even notice this air pressure adjustment, your body has access to about 25 percent less oxygen than at sea level. Those who are not used to it may experience dizziness or lightheadedness. They might even faint.
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To combat this risk, flight crews turn down the heat. Not only does cold air keep passengers more alert, essential for responding to sudden turbulence or efficient evacuation, but warm temperatures make it harder for the body to maintain circulation and cause the heart to pump faster, requiring more oxygen.
Cold air, on the other hand, helps slow your heart rate, keeps breathing stable, and helps stabilize blood oxygen levels. It also prevents nausea and dizziness by calming the body’s temperature control system and balancing it.
Keeping the airplane cabin cooler also helps regulate the humidity inside, Laurie says. Typically, the already low cabin humidity levels would cause body moisture to evaporate more quickly and cause immediate dehydration. But pumping out the air prevents passengers from getting too hot, which slows evaporation. It also counteracts humidity vapor in the environment, making your environment feel less stuffy.
How body heat affects temperatures
Chances are, you’ll often find yourself packing on layers at the start of a long-haul flight, only to take off some of them somewhere over the Pacific. This is because having hundreds of passengers so close together in an enclosed cabin can really raise temperatures.
Think about it, Laurie says. You’re probably covered by a blanket. Maybe you’re putting on a hoodie to keep your head warm and the person next to you is literally inches away. “With everyone’s collective body heat,” he says, “you’ll probably start to feel very hot.”
Keeping the cabin cooler helps mitigate this natural flow of heat and keep everyone more comfortable in the long run.
Who controls the cabin temperature?
It depends on the type of plane. “Both Airbus and Boeing operate completely differently,” Laurie says. On Boeing airplanes, cabin temperature is controlled from the flight deck, also known as the cockpit. “So [pilots] “They’re adjusting the temperature to what they think it should be, but they haven’t actually gone back there.”
Airbus planes allow flight attendants to adjust actual cabin temperatures via a central touchscreen, while Boeing typically relies on rudimentary rotary knobs calibrated with general ranges from “cold” to “warm” rather than exact numerical values.
Still, all commercial aircraft have an integrated Environmental Control System (ECS) that manages the pressure, temperature and air quality of the aircraft cabin. An ECS distributes conditioned air to several different areas of the aircraft.
The flight deck has its own dedicated ECS zone, as this area of the aircraft is filled with heat-generating radar, communications and navigation equipment that requires dedicated cooling.
However, the passenger cabin is usually separated into two to four independently controlled temperature zones (for example: forward, middle and aft). This allows flight attendants to lower the air, for example, in the center cabin of the plane, which tends to generate the most body heat, while keeping the rear of the plane cool.
To control the temperature in each specific zone, airplanes use makeup air valves. These specialized components introduce small amounts of hot or cold air into the main airflow ducts, allowing for custom temperatures designed specifically for each localized zone.
“If you walk toward the back of the plane, you might even feel a change in the air once or twice,” Laurie says.
Where to sit if you are cold
Besides wearing a hoodie, there are other ways to escape the cold of the cabin. Avoid sitting in an exit row, as frigid air can seep through door seals. Window seats also tend to be cooler, since they are closer to the outside of the plane.
“The galleys,” those designated areas for cooking and preparation on an airplane, “are always colder than the rest of the plane,” Laurie says. Not only are they typically located near the door of an airplane, but they also house the powerful galley refrigeration units that airplanes use to store food.
Ultimately, everyone’s body temperature is different and the way heat is perceived varies. “Let’s say you’re on a domestic flight along with 150 to 200 other passengers,” Laurie says. “It’s going to be difficult to make everyone happy at the same time.” Instead, she suggests, pack your carry-on accordingly!
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