First, the air inside a commercial airplane feels cold because it's dry. With a relative humidity level of just 20%, airplane cabins feel colder than what they actually are. With that said, commercial airlines intentionally maintain cold air inside their cabins to protect passengers and crew members from hypoxia.

Airplanes are kept notoriously cold (usually between 18°C and 22°C) for a very specific medical reason: to prevent hypoxia-related fainting. Studies have shown that passengers are more likely to faint on a plane if the cabin is warm, primarily due to the lower air pressure and reduced oxygen levels at altitude. Keeping the cabin "chilly" helps keep passengers alert and reduces the risk of medical emergencies. Additionally, a cold cabin helps to neutralize odors in a confined space and inhibits the growth of bacteria. From a technical standpoint, it is much easier and faster for the plane's Environmental Control System (ECS) to heat a cold cabin than to cool down a hot one packed with 300 heat-generating humans. In 2026, most modern planes like the A350 use "zone-based" temperature control, but pilots still err on the side of "cold" to ensure passenger safety and comfort. This is why the "pro-tip" for 2026 remains the same as always: dress in layers and always bring a light jacket or pashmina, even if you are flying to a tropical destination.