Oh man, is this a sore spot for me! This is the oldest Flight Attendant trick in the book (and even dates back to train travel)! Some lazy FAs purposefully crank up the temp as they know it makes most passengers sleepy and sends them to la-la land which makes their job easier no longer having to serve awake and demanding passengers.

Pan Am FAs were notorious for this practice. I used to beg them to turn down the heat. One actually told me some passengers complained of cold. I told her, "Hey, they can put on more clothes or blankets, but what do you want me to do...strip down naked!?"

I can't sleep on a plane due to claustrophobia, and heat severely intensifies this condition.

I don't encounter this much anymore. But when it happens I keep on 'em until the turn it down.