Did you suppose that at a single point, airplanes existed without having a heating method in them? When we fly on airplanes, we rely heavily on the Heating, Ventilation and A/C device on the plane, and in fact, in most airplanes, there are various vents above each person’s head that allows cool air from the Heating, Ventilation and A/C device to keep us comfortable; Technically, airplanes mainly use a heating method on their plane.
They don’t truly need an a/c on the plane because the air outside is freezing cold at that height.
Without the Heating, Ventilation and A/C unit, most of us would have to bundle up because we would be unquestionably cold. In fact, people used to ride on planes before they installed furnaces on them. If you were the pilot of a plane before they had furnaces, you would have to wear thick suits to stay warm. It was even more difficult to be a passenger on a plane before the Heating, Ventilation and A/C units were created, then obviously, back then, planes were not used for public travel which is why Heating, Ventilation and A/C units were not necessary. However, I am thankful that they have Heating, Ventilation and A/C units on planes now. I travel on a plane various times per year, plus I would never want to have to sit in a plane without a heating method to keep me warm. I care about that most planes are warm, plus they have the vent in the Heating, Ventilation and A/C device that pumps in the cold air from outside. The ability to be able to control the temperature in each seat is nice. I wouldn’t ever want to go back.