Layer up
You can’t predict the temperature on the plane. You could stuff your carry-on with a blanket to prepare, but that takes too much space. No one wants to be too hot or cold, so wear layers instead. This way, when you are in the air, you have options.
Like an onion, you will have many layers to warm you up if the temperature drops. You can also take off your jacket or sweatshirt if you get hot. A bonus of this trick is that you have extra pockets to carry more things you couldn’t fit in your carry-on.