Why is it always so cold on airplanes?

As soon as you've found your seat and buckled up, the chills begin to set in. The air conditioning roars, a cool blast of air hits your forehead—and the sweater in your carry-on luggage becomes your best travel companion.

Anyone who flies a lot will be familiar with this phenomenon: While the sun is blazing outside and temperatures are 35 degrees Celsius at your destination, you regularly shiver above the clouds like it's late autumn. But why?

A technical defect? Rather rare. Malicious intent on the part of the airline? Hardly. A conspiracy against shorts and T-shirts? Of course not—even if it sometimes feels that way.

The Logic of the Chill

There’s a good reason airline cabins often feel chilly—and it’s not just to make you shiver. At cruising altitude, air pressure and oxygen levels are lower, putting extra strain on the circulatory system. Warmer cabin temperatures could worsen that effect, so airlines keep the air slightly cooler to help passengers’ bodies stay stable during long periods of sitting.

The cooling is also a by-product of the aircraft’s ventilation system, which draws in frigid, thin outside air and heats it unevenly. Depending on your seat location, you might feel comfortably fresh—or uncomfortably cold. There’s another benefit too: cooler air can help slow the spread of germs, a welcome precaution on crowded flights.

In short, the chill is deliberate—not cruel, but practical. If you’re prepared, you’ll be far more comfortable. That T-shirt you wore at the gate might need backup once you’re airborne: a sweater, a scarf, or even the thin blanket most airlines still provide.