Bring your own blanket
Every airline has its own branded blanket for when you board the plane. Despite coming in a sealed bag, somebody else used it on a previous flight. The airline probably quickly washes it, puts it in a plastic bag, and seals it before giving it to you.
We can’t be sure how clean it is, and after all, airplane blankets aren’t warm enough. That is why you should travel with a small blanket. A blanket is essential if you don’t layer your clothes and are always cold on flights. This is also great to carry if you’re traveling with children.