Why airlines keep cabins colder than normal

HostI was on a flight last week and had to wear my heavy coat just to stop shivering. It feels like I'm sitting in a walk-in fridge every time I fly. Why do they not just turn the heat up a few notches?

GuestIt actually comes down to keeping you awake and alert. There was a study that showed a real link between how warm a plane is and how likely people are to pass out. If the air gets even a little bit too warm, people start fainting in their seats. Most people think it's just about saving money on the heater, but it's really a medical choice.

HostPassing out? People don't just fall over because it's seventy-five degrees in a room.

GuestOn the ground, you're right, seventy-five degrees is fine. But in a plane, your body is already working a lot harder just to stay steady. Even though the air inside is pumped in, it's still much thinner than what we're used to on the ground. You have less oxygen in your blood than usual. When you combine that with a warm room, it triggers a reaction in your heart and lungs. Your blood vessels grow wide to try and cool you down, which makes your blood pressure drop fast. In that thin air, your brain doesn't get what it needs to stay awake, and you go limp.

HostSo it's a safety tool. But why is there no middle ground?

GuestEveryone's body reacts differently. What feels like a nice spring day to you might be a heatwave for the person next to you. Since the crew can't track how everyone feels, they go with the low end of the scale. It's much easier to give you a blanket than it's to deal with a medical emergency because three people fainted at the same time.

HostWhat about that old air feeling? Does the cold help there?

GuestIt's a trick of the mind. When air is warm and still, we feel like it's dirty or used up. Cold air feels crisp and fresh. Since you're packed in with hundreds of other people, that feeling of freshness keeps people calm. If it was eighty degrees in there, people would start feeling trapped or panicky pretty fast.

HostBut even when the screen says it's room temp, I feel freezing.

GuestYou aren't imagining it, it's the lack of water in the air. On the ground, the air has some moisture in it which helps hold heat against your skin. But way up there, the air is bone dry. It's like a desert. When there's no water in the air, sweat dries off your skin much faster, which pulls heat away from your body. Sixty-eight degrees on a plane feels way colder than sixty-eight degrees in your house. It's like the difference between a desert and a swamp. Without that water in the air, your body can't hold onto its own warmth, so you're basically leaking heat into the cabin every second you sit there.

HostSo the dry air and the safety rules are ganging up on us.

GuestAnd you aren't moving. On a plane, you're strapped into a chair for hours. Your blood flow slows down because your legs aren't moving. That makes your hands and feet feel like ice blocks while your core stays warm.

HostWhy not just spray some water into the vents?

GuestIt would rot the plane. All that water would turn into tiny drops on the cold metal skin of the plane and cause rust. Airlines would rather you wear a sweater than have to fix a rust spot caused by damp air. Plus, water is incredibly heavy. To keep a big plane moist for a long flight, you would need to carry hundreds of pounds of water. That weight burns a lot of extra fuel, which makes tickets more expensive.

HostDo the newer planes actually feel better?

GuestSome new planes are made of carbon fiber instead of metal. Since that stuff doesn't rust, they can keep the air a bit more moist. It's still chilly, but you won't feel quite as much like a piece of dried fruit by the time you land.

HostThe flight attendants always seem fine, though.

GuestThey're walking up and down the aisles and lifting bags. Their bodies are making plenty of heat. If it was warm enough for you to be cozy, the crew would be sweating through their shirts in ten minutes.

HostSo it's safety, the plane's health, and the crew.

GuestAnd it keeps people from getting sick. Warmth and a bumpy ride don't go well together for your stomach. Keeping the cabin brisk is one of the simplest ways to keep everyone's lunch down.

HostEvery degree is a choice to keep us safe, even if we're shivering.

GuestThose thin blankets are the last line of defense against a body that just wants to shut down when the air gets thin and the room gets cozy.

HostThat heavy coat is staying in my bag from now on, knowing it's the only thing keeping me from a very sudden and very public nap.