Many new planes like most 777s and Airbus A340-500s do not have personal air vents, so you cannot control your personal body temperature. So if you get warm you have to take off your shirt, and possibly your pants so you may end up in your underwear to avoid passing out if you personally get too warm. I actually recently purchased a battery operated fan to avoid the pants removal. I few years back on a trans-Atlantic flight on a 777 with no personal air vents, I became so warm I requested the crew to land the plane or decrease cabin temperature becasue in the cramped seat I was ready to pass out. They decreased the cabin temperature which made other passengers too cold. If the plane has personal air vents, no matter how warm the plane gets, I can always manage to maintain a healthy personal body temperature by directing the vent towards me. Those passengers who like a wamer plane are also comfortable.

For those passengers who become too warm on a plane, it is a health issue.