Recently on a super hot and humid day, I caught myself frantically digging through my backpack for a shawl because my legs will no longer walk into an airplane without "cover" in my hand. The average temperature in an airplane cabin is 22 to 24 degrees C, i.e., 71-75 degrees F. So what's not to like about that? Well, the low-end of the range can be 18C, i.e., 64.4F. Brain freeze alert!

In the cabin, I feel like bacteria in a petri dish and I protest. If you do too, raise your hand.
Turns out some of us still function at higher temps. We don't overheat easily but we freeze faster than water droplets at 35,000 feet. I blame hormones for all my troubles, especially since my metabolism went into a deep freeze and my ability to handle cold temperatures died an ignominious death.
I beg you, please quit blasting me with cold air.
On my last plane ride, passengers around me were sitting with arms crossed at their chest, trying to hug themselves back to 98.6F. With a megawatt smile, I whipped out my shawl, flicked it over my shoulders, tucked my arms underneath, and promptly fell asleep. I don't care how hot it is outside, you will not find me sans shawl in an airplane.
Somedays I think the Wright Brothers had the right idea. Open air ventilation. Don't go too high. Don't get too cold. Boeing 737s and Airbus 320s, the workhorses on domestic routes, fly at an average altitude of 30-35K feet. The outside temperature at that altitude hovers at a -51C. Brrr.

So, cabins have to be heated to the freezing temps we encounter when we fly!
Add 100 or 200 odd passengers all spewing heat when packed into an enclosed space and aircrafts allegedly can become furnaces. I have to admit that I am yet to encounter said furnace. But, I will try to remember the outside temperature when I fly the next time and hopefully that will warm me up.
The scientific reason for cold cabins is to prevent hypoxia - fainting due to low oxygen and high temperatures. It's a real thing apparently. The choice of freezing vs. lack of oxygenation is a tough one to navigate.
The Journal of Environmental Health Research cites that compared to life on the ground, cold bugs are 113 times more likely to transmit in an airplane. Speedy little buggers. I have always blamed being too cold in the aircraft for post-travel illness. Turns out that the reason for this is not the chill, it is because airplane cabins have incredibly low humidity since the outside air at cruising altitude is drier than sand paper. While the cold blast from above chills us to the bones, the dry air renders our airway defenseless against microbes. Ugh.
Even when I am headed to a tropical isle in a pair of shorts, t-shirt, and flip flops, I have heavy cover to keep warm on the way and I drink gallons of water to keep my airway slick. Granted that I look like a dork and go to the restroom every 15 minutes, but I arrive alive.
Bundle up friends 'cos the chill is better than the alternative.
